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	$92.35	13.842%	$105.1331	$105.13	$105.15	$105.10
Purchase #2	$89.27	3.106%	$92.0427	$92.04	$92.05	$92.00
Purchase #3	$68.48	3.286%	$70.7303	$70.73	$70.75	$70.70
Purchase #4	$91.71	9.602%	$100.516	$100.52	$100.50	$100.50
Purchase #5	$124.70	4.726%	$130.5933	$130.59	$130.60	$130.60
Purchase #6	$247.41	9.729%	$271.4805	$271.48	$271.50	$271.50
Purchase #7	$190.67	8.236%	$206.3736	$206.37	$206.35	$206.40
7 purchase totals =	$904.59		$976.8695	$976.86	$976.90	$976.80