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	$148.93	11.190%	$165.5953	$165.60	$165.60	$165.60
Purchase #2	$214.47	13.743%	$243.9446	$243.94	$243.95	$243.90
Purchase #3	$125.86	5.141%	$132.3305	$132.33	$132.35	$132.30
Purchase #4	$149.28	11.117%	$165.8755	$165.88	$165.90	$165.90
Purchase #5	$180.53	5.426%	$190.3256	$190.33	$190.35	$190.30
Purchase #6	$173.26	6.545%	$184.5999	$184.60	$184.60	$184.60
Purchase #7	$20.25	12.363%	$22.7535	$22.75	$22.75	$22.80
7 purchase totals =	$1,012.58		$1,105.4249	$1,105.43	$1,105.50	$1,105.40