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	$188.40	13.358%	$213.5665	$213.57	$213.55	$213.60
Purchase #2	$70.87	9.459%	$77.5736	$77.57	$77.55	$77.60
Purchase #3	$66.62	8.808%	$72.4879	$72.49	$72.50	$72.50
Purchase #4	$138.50	9.332%	$151.4248	$151.42	$151.40	$151.40
Purchase #5	$77.61	8.103%	$83.8987	$83.90	$83.90	$83.90
Purchase #6	$246.63	4.764%	$258.3795	$258.38	$258.40	$258.40
Purchase #7	$82.59	5.753%	$87.3414	$87.34	$87.35	$87.30
7 purchase totals =	$871.22		$944.6724	$944.67	$944.65	$944.70