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	$237.72	7.616%	$255.8248	$255.82	$255.80	$255.80
Purchase #2	$70.43	6.231%	$74.8185	$74.82	$74.80	$74.80
Purchase #3	$52.75	5.213%	$55.4999	$55.50	$55.50	$55.50
Purchase #4	$216.85	7.793%	$233.7491	$233.75	$233.75	$233.70
Purchase #5	$82.90	13.319%	$93.9415	$93.94	$93.95	$93.90
Purchase #6	$173.48	6.592%	$184.9158	$184.92	$184.90	$184.90
Purchase #7	$201.85	13.252%	$228.5992	$228.60	$228.60	$228.60
7 purchase totals =	$1,035.98		$1,127.3488	$1,127.35	$1,127.30	$1,127.20