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	$58.73	4.677%	$61.4768	$61.48	$61.50	$61.50
Purchase #2	$41.56	4.810%	$43.559	$43.56	$43.55	$43.60
Purchase #3	$85.64	8.640%	$93.0393	$93.04	$93.05	$93.00
Purchase #4	$40.96	12.171%	$45.9452	$45.95	$45.95	$45.90
Purchase #5	$137.70	7.804%	$148.4461	$148.45	$148.45	$148.40
Purchase #6	$127.68	5.655%	$134.9003	$134.90	$134.90	$134.90
Purchase #7	$175.84	5.485%	$185.4848	$185.48	$185.50	$185.50
7 purchase totals =	$668.11		$712.8515	$712.86	$712.90	$712.80