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	$135.72	10.715%	$150.2624	$150.26	$150.25	$150.30
Purchase #2	$196.58	7.554%	$211.4297	$211.43	$211.45	$211.40
Purchase #3	$50.76	5.374%	$53.4878	$53.49	$53.50	$53.50
Purchase #4	$190.56	13.420%	$216.1332	$216.13	$216.15	$216.10
Purchase #5	$93.70	13.426%	$106.2802	$106.28	$106.30	$106.30
Purchase #6	$121.69	3.106%	$125.4697	$125.47	$125.45	$125.50
Purchase #7	$199.75	11.557%	$222.8351	$222.84	$222.85	$222.80
7 purchase totals =	$988.76		$1,085.8981	$1,085.90	$1,085.95	$1,085.90