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	$111.63	10.327%	$123.158	$123.16	$123.15	$123.20
Purchase #2	$64.33	13.710%	$73.1496	$73.15	$73.15	$73.10
Purchase #3	$109.72	13.277%	$124.2875	$124.29	$124.30	$124.30
Purchase #4	$222.70	10.501%	$246.0857	$246.09	$246.10	$246.10
Purchase #5	$115.74	7.279%	$124.1647	$124.16	$124.15	$124.20
Purchase #6	$117.58	12.139%	$131.853	$131.85	$131.85	$131.90
Purchase #7	$89.99	4.481%	$94.0225	$94.02	$94.00	$94.00
7 purchase totals =	$831.69		$916.7210	$916.72	$916.70	$916.80