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	$153.96	3.433%	$159.2454	$159.25	$159.25	$159.20
Purchase #2	$81.94	4.130%	$85.3241	$85.32	$85.30	$85.30
Purchase #3	$33.62	12.518%	$37.8286	$37.83	$37.85	$37.80
Purchase #4	$42.36	6.439%	$45.0876	$45.09	$45.10	$45.10
Purchase #5	$158.29	4.306%	$165.106	$165.11	$165.10	$165.10
Purchase #6	$207.94	10.548%	$229.8735	$229.87	$229.85	$229.90
Purchase #7	$181.38	12.603%	$204.2393	$204.24	$204.25	$204.20
7 purchase totals =	$859.49		$926.7045	$926.71	$926.70	$926.60