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	$131.60	3.723%	$136.4995	$136.50	$136.50	$136.50
Purchase #2	$59.34	8.336%	$64.2866	$64.29	$64.30	$64.30
Purchase #3	$148.72	5.155%	$156.3865	$156.39	$156.40	$156.40
Purchase #4	$162.32	11.317%	$180.6898	$180.69	$180.70	$180.70
Purchase #5	$132.93	5.288%	$139.9593	$139.96	$139.95	$140.00
Purchase #6	$212.38	10.424%	$234.5185	$234.52	$234.50	$234.50
Purchase #7	$221.43	13.863%	$252.1268	$252.13	$252.15	$252.10
7 purchase totals =	$1,068.72		$1,164.4670	$1,164.48	$1,164.50	$1,164.50