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	$82.43	8.840%	$89.7168	$89.72	$89.70	$89.70
Purchase #2	$148.95	4.523%	$155.687	$155.69	$155.70	$155.70
Purchase #3	$159.82	9.635%	$175.2187	$175.22	$175.20	$175.20
Purchase #4	$173.84	10.385%	$191.8933	$191.89	$191.90	$191.90
Purchase #5	$148.82	12.538%	$167.4791	$167.48	$167.50	$167.50
Purchase #6	$178.96	8.197%	$193.6294	$193.63	$193.65	$193.60
Purchase #7	$121.56	12.745%	$137.0528	$137.05	$137.05	$137.10
7 purchase totals =	$1,014.38		$1,110.6771	$1,110.68	$1,110.70	$1,110.70