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	$37.52	11.256%	$41.7433	$41.74	$41.75	$41.70
Purchase #2	$136.40	5.168%	$143.4492	$143.45	$143.45	$143.40
Purchase #3	$139.57	5.118%	$146.7132	$146.71	$146.70	$146.70
Purchase #4	$54.56	10.196%	$60.1229	$60.12	$60.10	$60.10
Purchase #5	$36.33	9.295%	$39.7069	$39.71	$39.70	$39.70
Purchase #6	$116.86	5.411%	$123.1833	$123.18	$123.20	$123.20
Purchase #7	$220.71	11.193%	$245.4141	$245.41	$245.40	$245.40
7 purchase totals =	$741.95		$800.3329	$800.32	$800.30	$800.20