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	$218.44	10.733%	$241.8852	$241.89	$241.90	$241.90
Purchase #2	$249.48	6.403%	$265.4542	$265.45	$265.45	$265.50
Purchase #3	$116.90	6.184%	$124.1291	$124.13	$124.15	$124.10
Purchase #4	$187.89	11.152%	$208.8435	$208.84	$208.85	$208.80
Purchase #5	$218.60	12.454%	$245.8244	$245.82	$245.80	$245.80
Purchase #6	$233.90	9.664%	$256.5041	$256.50	$256.50	$256.50
Purchase #7	$67.88	4.812%	$71.1464	$71.15	$71.15	$71.10
7 purchase totals =	$1,293.09		$1,413.7869	$1,413.78	$1,413.80	$1,413.70