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	$206.61	7.682%	$222.4818	$222.48	$222.50	$222.50
Purchase #2	$79.65	13.706%	$90.5668	$90.57	$90.55	$90.60
Purchase #3	$26.54	6.222%	$28.1913	$28.19	$28.20	$28.20
Purchase #4	$91.50	6.210%	$97.1822	$97.18	$97.20	$97.20
Purchase #5	$116.52	6.718%	$124.3478	$124.35	$124.35	$124.30
Purchase #6	$141.87	8.476%	$153.8949	$153.89	$153.90	$153.90
Purchase #7	$19.52	11.179%	$21.7021	$21.70	$21.70	$21.70
7 purchase totals =	$682.21		$738.3669	$738.36	$738.40	$738.40