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	$172.45	11.510%	$192.299	$192.30	$192.30	$192.30
Purchase #2	$79.70	11.503%	$88.8679	$88.87	$88.85	$88.90
Purchase #3	$131.52	5.190%	$138.3459	$138.35	$138.35	$138.30
Purchase #4	$76.94	4.160%	$80.1407	$80.14	$80.15	$80.10
Purchase #5	$144.95	7.358%	$155.6154	$155.62	$155.60	$155.60
Purchase #6	$186.82	5.234%	$196.5982	$196.60	$196.60	$196.60
Purchase #7	$232.85	8.813%	$253.3711	$253.37	$253.35	$253.40
7 purchase totals =	$1,025.23		$1,105.2382	$1,105.25	$1,105.20	$1,105.20