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	$77.43	5.312%	$81.5431	$81.54	$81.55	$81.50
Purchase #2	$181.81	12.421%	$204.3926	$204.39	$204.40	$204.40
Purchase #3	$153.58	7.533%	$165.1492	$165.15	$165.15	$165.10
Purchase #4	$151.64	4.390%	$158.297	$158.30	$158.30	$158.30
Purchase #5	$149.82	12.702%	$168.8501	$168.85	$168.85	$168.90
Purchase #6	$53.42	10.542%	$59.0515	$59.05	$59.05	$59.10
Purchase #7	$96.69	12.433%	$108.7115	$108.71	$108.70	$108.70
7 purchase totals =	$864.39		$945.9950	$945.99	$946.00	$946.00