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	$140.38	8.182%	$151.8659	$151.87	$151.85	$151.90
Purchase #2	$148.51	12.668%	$167.3232	$167.32	$167.30	$167.30
Purchase #3	$25.64	12.465%	$28.836	$28.84	$28.85	$28.80
Purchase #4	$98.63	9.612%	$108.1103	$108.11	$108.10	$108.10
Purchase #5	$236.95	7.366%	$254.4037	$254.40	$254.40	$254.40
Purchase #6	$95.71	4.438%	$99.9576	$99.96	$99.95	$100.00
Purchase #7	$105.77	5.563%	$111.654	$111.65	$111.65	$111.70
7 purchase totals =	$851.59		$922.1507	$922.15	$922.10	$922.20