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	$248.81	13.341%	$282.0037	$282.00	$282.00	$282.00
Purchase #2	$100.97	10.581%	$111.6536	$111.65	$111.65	$111.70
Purchase #3	$63.64	11.838%	$71.1737	$71.17	$71.15	$71.20
Purchase #4	$248.30	5.723%	$262.5102	$262.51	$262.50	$262.50
Purchase #5	$61.46	9.854%	$67.5163	$67.52	$67.50	$67.50
Purchase #6	$149.85	7.266%	$160.7381	$160.74	$160.75	$160.70
Purchase #7	$243.54	8.200%	$263.5103	$263.51	$263.50	$263.50
7 purchase totals =	$1,116.57		$1,219.1059	$1,219.10	$1,219.05	$1,219.10