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	$200.82	12.498%	$225.9185	$225.92	$225.90	$225.90
Purchase #2	$90.57	9.556%	$99.2249	$99.22	$99.20	$99.20
Purchase #3	$205.95	12.204%	$231.0841	$231.08	$231.10	$231.10
Purchase #4	$19.81	13.371%	$22.4588	$22.46	$22.45	$22.50
Purchase #5	$86.57	9.688%	$94.9569	$94.96	$94.95	$95.00
Purchase #6	$153.77	7.185%	$164.8184	$164.82	$164.80	$164.80
Purchase #7	$33.74	11.153%	$37.503	$37.50	$37.50	$37.50
7 purchase totals =	$791.23		$875.9646	$875.96	$875.90	$876.00