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	$148.42	13.508%	$168.4686	$168.47	$168.45	$168.50
Purchase #2	$249.55	7.120%	$267.318	$267.32	$267.30	$267.30
Purchase #3	$218.89	6.208%	$232.4787	$232.48	$232.50	$232.50
Purchase #4	$118.31	5.456%	$124.765	$124.77	$124.75	$124.80
Purchase #5	$32.57	3.229%	$33.6217	$33.62	$33.60	$33.60
Purchase #6	$203.40	6.746%	$217.1214	$217.12	$217.10	$217.10
Purchase #7	$21.87	11.792%	$24.4489	$24.45	$24.45	$24.40
7 purchase totals =	$993.01		$1,068.2223	$1,068.23	$1,068.15	$1,068.20