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	$49.55	7.408%	$53.2207	$53.22	$53.20	$53.20
Purchase #2	$88.54	7.689%	$95.3478	$95.35	$95.35	$95.30
Purchase #3	$126.33	6.375%	$134.3835	$134.38	$134.40	$134.40
Purchase #4	$30.77	5.221%	$32.3765	$32.38	$32.40	$32.40
Purchase #5	$187.72	4.487%	$196.143	$196.14	$196.15	$196.10
Purchase #6	$94.58	7.105%	$101.2999	$101.30	$101.30	$101.30
Purchase #7	$171.39	6.680%	$182.8389	$182.84	$182.85	$182.80
7 purchase totals =	$748.88		$795.6103	$795.61	$795.65	$795.50