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	$66.47	9.118%	$72.5307	$72.53	$72.55	$72.50
Purchase #2	$236.86	11.817%	$264.8497	$264.85	$264.85	$264.80
Purchase #3	$204.50	12.624%	$230.3161	$230.32	$230.30	$230.30
Purchase #4	$81.57	11.409%	$90.8763	$90.88	$90.90	$90.90
Purchase #5	$210.56	7.777%	$226.9353	$226.94	$226.95	$226.90
Purchase #6	$75.85	9.813%	$83.2932	$83.29	$83.30	$83.30
Purchase #7	$185.73	9.713%	$203.77	$203.77	$203.75	$203.80
7 purchase totals =	$1,061.54		$1,172.5713	$1,172.58	$1,172.60	$1,172.50