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	$179.79	11.644%	$200.7247	$200.72	$200.70	$200.70
Purchase #2	$148.89	8.732%	$161.8911	$161.89	$161.90	$161.90
Purchase #3	$37.36	7.556%	$40.1829	$40.18	$40.20	$40.20
Purchase #4	$234.61	4.707%	$245.6531	$245.65	$245.65	$245.70
Purchase #5	$31.34	7.605%	$33.7234	$33.72	$33.70	$33.70
Purchase #6	$53.62	10.685%	$59.3493	$59.35	$59.35	$59.30
Purchase #7	$135.96	13.275%	$154.0087	$154.01	$154.00	$154.00
7 purchase totals =	$821.57		$895.5332	$895.52	$895.50	$895.50