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	$231.60	13.350%	$262.5186	$262.52	$262.50	$262.50
Purchase #2	$168.52	8.387%	$182.6538	$182.65	$182.65	$182.70
Purchase #3	$85.50	13.336%	$96.9023	$96.90	$96.90	$96.90
Purchase #4	$200.70	12.504%	$225.7955	$225.80	$225.80	$225.80
Purchase #5	$129.78	9.715%	$142.3881	$142.39	$142.40	$142.40
Purchase #6	$122.95	3.414%	$127.1475	$127.15	$127.15	$127.10
Purchase #7	$22.62	10.148%	$24.9155	$24.92	$24.90	$24.90
7 purchase totals =	$961.67		$1,062.3213	$1,062.33	$1,062.30	$1,062.30