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	$57.59	7.232%	$61.7549	$61.75	$61.75	$61.80
Purchase #2	$238.54	8.490%	$258.792	$258.79	$258.80	$258.80
Purchase #3	$82.87	3.279%	$85.5873	$85.59	$85.60	$85.60
Purchase #4	$224.52	7.523%	$241.4106	$241.41	$241.40	$241.40
Purchase #5	$60.93	6.715%	$65.0214	$65.02	$65.00	$65.00
Purchase #6	$62.40	6.519%	$66.4679	$66.47	$66.45	$66.50
Purchase #7	$93.61	11.733%	$104.5933	$104.59	$104.60	$104.60
7 purchase totals =	$820.46		$883.6274	$883.62	$883.60	$883.70