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	$171.26	8.344%	$185.5499	$185.55	$185.55	$185.50
Purchase #2	$240.77	12.802%	$271.5934	$271.59	$271.60	$271.60
Purchase #3	$158.72	9.460%	$173.7349	$173.73	$173.75	$173.70
Purchase #4	$55.60	11.312%	$61.8895	$61.89	$61.90	$61.90
Purchase #5	$130.43	13.747%	$148.3602	$148.36	$148.35	$148.40
Purchase #6	$41.62	5.810%	$44.0381	$44.04	$44.05	$44.00
Purchase #7	$157.44	11.330%	$175.278	$175.28	$175.30	$175.30
7 purchase totals =	$955.84		$1,060.4440	$1,060.44	$1,060.50	$1,060.40