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	$231.95	8.841%	$252.4567	$252.46	$252.45	$252.50
Purchase #2	$108.39	6.160%	$115.0668	$115.07	$115.05	$115.10
Purchase #3	$66.77	8.219%	$72.2578	$72.26	$72.25	$72.30
Purchase #4	$84.87	6.418%	$90.317	$90.32	$90.30	$90.30
Purchase #5	$59.36	12.537%	$66.802	$66.80	$66.80	$66.80
Purchase #6	$96.50	9.767%	$105.9252	$105.93	$105.95	$105.90
Purchase #7	$48.68	3.505%	$50.3862	$50.39	$50.40	$50.40
7 purchase totals =	$696.52		$753.2117	$753.23	$753.20	$753.30