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	$238.58	5.105%	$250.7595	$250.76	$250.75	$250.80
Purchase #2	$202.35	10.130%	$222.8481	$222.85	$222.85	$222.80
Purchase #3	$216.31	8.361%	$234.3957	$234.40	$234.40	$234.40
Purchase #4	$124.37	12.813%	$140.3055	$140.31	$140.30	$140.30
Purchase #5	$145.84	5.800%	$154.2987	$154.30	$154.30	$154.30
Purchase #6	$99.96	11.778%	$111.7333	$111.73	$111.75	$111.70
Purchase #7	$133.48	6.852%	$142.626	$142.63	$142.65	$142.60
7 purchase totals =	$1,160.89		$1,256.9668	$1,256.98	$1,257.00	$1,256.90