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	$38.72	11.467%	$43.16	$43.16	$43.15	$43.20
Purchase #2	$40.81	10.473%	$45.084	$45.08	$45.10	$45.10
Purchase #3	$37.34	7.497%	$40.1394	$40.14	$40.15	$40.10
Purchase #4	$135.86	6.438%	$144.6067	$144.61	$144.60	$144.60
Purchase #5	$8.81	9.602%	$9.6559	$9.66	$9.65	$9.70
Purchase #6	$89.57	10.790%	$99.2346	$99.23	$99.25	$99.20
Purchase #7	$53.84	5.441%	$56.7694	$56.77	$56.75	$56.80
7 purchase totals =	$404.95		$438.6500	$438.65	$438.65	$438.70