Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$141.63	9.328%	$154.8412	$154.84	$154.85	$154.80
Purchase #2	$198.57	8.556%	$215.5596	$215.56	$215.55	$215.60
Purchase #3	$99.66	12.207%	$111.8255	$111.83	$111.85	$111.80
Purchase #4	$113.53	12.349%	$127.5498	$127.55	$127.55	$127.50
Purchase #5	$163.38	5.348%	$172.1176	$172.12	$172.10	$172.10
Purchase #6	$8.30	10.830%	$9.1989	$9.20	$9.20	$9.20
Purchase #7	$99.88	11.473%	$111.3392	$111.34	$111.35	$111.30
7 purchase totals =	$824.95		$902.4318	$902.44	$902.45	$902.30