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	$185.65	7.229%	$199.0706	$199.07	$199.05	$199.10
Purchase #2	$27.91	13.657%	$31.7217	$31.72	$31.70	$31.70
Purchase #3	$147.53	12.408%	$165.8355	$165.84	$165.85	$165.80
Purchase #4	$196.69	10.367%	$217.0809	$217.08	$217.10	$217.10
Purchase #5	$166.25	7.580%	$178.8518	$178.85	$178.85	$178.90
Purchase #6	$211.89	5.341%	$223.207	$223.21	$223.20	$223.20
Purchase #7	$65.48	10.251%	$72.1924	$72.19	$72.20	$72.20
7 purchase totals =	$1,001.40		$1,087.9599	$1,087.96	$1,087.95	$1,088.00