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	$22.46	13.491%	$25.4901	$25.49	$25.50	$25.50
Purchase #2	$227.90	6.716%	$243.2058	$243.21	$243.20	$243.20
Purchase #3	$200.46	4.754%	$209.9899	$209.99	$210.00	$210.00
Purchase #4	$151.31	9.447%	$165.6043	$165.60	$165.60	$165.60
Purchase #5	$68.28	5.369%	$71.946	$71.95	$71.95	$71.90
Purchase #6	$72.89	13.815%	$82.9598	$82.96	$82.95	$83.00
Purchase #7	$231.49	9.858%	$254.3103	$254.31	$254.30	$254.30
7 purchase totals =	$974.79		$1,053.5062	$1,053.51	$1,053.50	$1,053.50