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	$12.77	8.466%	$13.8511	$13.85	$13.85	$13.90
Purchase #2	$65.29	9.721%	$71.6368	$71.64	$71.65	$71.60
Purchase #3	$231.41	5.151%	$243.3299	$243.33	$243.35	$243.30
Purchase #4	$134.83	11.208%	$149.9417	$149.94	$149.95	$149.90
Purchase #5	$38.43	5.825%	$40.6685	$40.67	$40.65	$40.70
Purchase #6	$98.42	6.642%	$104.9571	$104.96	$104.95	$105.00
Purchase #7	$123.83	12.439%	$139.2332	$139.23	$139.25	$139.20
7 purchase totals =	$704.98		$763.6183	$763.62	$763.65	$763.60