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	$101.63	9.518%	$111.3031	$111.30	$111.30	$111.30
Purchase #2	$191.90	13.646%	$218.0867	$218.09	$218.10	$218.10
Purchase #3	$54.58	12.105%	$61.1869	$61.19	$61.20	$61.20
Purchase #4	$223.96	7.387%	$240.5039	$240.50	$240.50	$240.50
Purchase #5	$41.78	8.570%	$45.3605	$45.36	$45.35	$45.40
Purchase #6	$85.72	5.644%	$90.558	$90.56	$90.55	$90.60
Purchase #7	$7.51	6.133%	$7.9706	$7.97	$7.95	$8.00
7 purchase totals =	$707.08		$774.9697	$774.97	$774.95	$775.10