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	$142.54	5.560%	$150.4652	$150.47	$150.45	$150.50
Purchase #2	$161.97	7.819%	$174.6344	$174.63	$174.65	$174.60
Purchase #3	$93.71	6.847%	$100.1263	$100.13	$100.15	$100.10
Purchase #4	$65.68	11.772%	$73.4118	$73.41	$73.40	$73.40
Purchase #5	$144.35	6.365%	$153.5379	$153.54	$153.55	$153.50
Purchase #6	$198.80	9.342%	$217.3719	$217.37	$217.35	$217.40
Purchase #7	$86.56	11.859%	$96.8252	$96.83	$96.85	$96.80
7 purchase totals =	$893.61		$966.3727	$966.38	$966.40	$966.30