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	$118.52	6.229%	$125.9026	$125.90	$125.90	$125.90
Purchase #2	$57.59	4.385%	$60.1153	$60.12	$60.10	$60.10
Purchase #3	$216.89	7.595%	$233.3628	$233.36	$233.35	$233.40
Purchase #4	$225.49	11.283%	$250.932	$250.93	$250.95	$250.90
Purchase #5	$98.83	5.319%	$104.0868	$104.09	$104.10	$104.10
Purchase #6	$105.43	13.236%	$119.3847	$119.38	$119.40	$119.40
Purchase #7	$172.52	7.184%	$184.9138	$184.91	$184.90	$184.90
7 purchase totals =	$995.27		$1,078.6980	$1,078.69	$1,078.70	$1,078.70