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	$215.66	12.261%	$242.1021	$242.10	$242.10	$242.10
Purchase #2	$142.73	8.671%	$155.1061	$155.11	$155.10	$155.10
Purchase #3	$222.29	3.191%	$229.3833	$229.38	$229.40	$229.40
Purchase #4	$131.27	11.852%	$146.8281	$146.83	$146.85	$146.80
Purchase #5	$55.61	10.545%	$61.4741	$61.47	$61.45	$61.50
Purchase #6	$136.52	5.415%	$143.9126	$143.91	$143.90	$143.90
Purchase #7	$209.63	3.457%	$216.8769	$216.88	$216.90	$216.90
7 purchase totals =	$1,113.71		$1,195.6832	$1,195.68	$1,195.70	$1,195.70