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	$108.54	7.518%	$116.7	$116.70	$116.70	$116.70
Purchase #2	$15.95	13.675%	$18.1312	$18.13	$18.15	$18.10
Purchase #3	$179.55	6.575%	$191.3554	$191.36	$191.35	$191.40
Purchase #4	$32.37	4.639%	$33.8716	$33.87	$33.85	$33.90
Purchase #5	$221.27	13.375%	$250.8649	$250.86	$250.85	$250.90
Purchase #6	$57.69	12.316%	$64.7951	$64.80	$64.80	$64.80
Purchase #7	$83.34	9.352%	$91.134	$91.13	$91.15	$91.10
7 purchase totals =	$698.71		$766.8522	$766.85	$766.85	$766.90