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	$202.88	13.675%	$230.6238	$230.62	$230.60	$230.60
Purchase #2	$205.25	5.638%	$216.822	$216.82	$216.80	$216.80
Purchase #3	$185.73	12.835%	$209.5684	$209.57	$209.55	$209.60
Purchase #4	$194.30	7.844%	$209.5409	$209.54	$209.55	$209.50
Purchase #5	$152.74	11.411%	$170.1692	$170.17	$170.15	$170.20
Purchase #6	$130.65	12.322%	$146.7487	$146.75	$146.75	$146.70
Purchase #7	$12.42	8.760%	$13.508	$13.51	$13.50	$13.50
7 purchase totals =	$1,083.97		$1,196.9810	$1,196.98	$1,196.90	$1,196.90