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	$31.29	5.341%	$32.9612	$32.96	$32.95	$33.00
Purchase #2	$27.76	12.701%	$31.2858	$31.29	$31.30	$31.30
Purchase #3	$99.98	5.392%	$105.3709	$105.37	$105.35	$105.40
Purchase #4	$37.47	11.606%	$41.8188	$41.82	$41.80	$41.80
Purchase #5	$229.81	5.285%	$241.9555	$241.96	$241.95	$242.00
Purchase #6	$221.48	3.285%	$228.7556	$228.76	$228.75	$228.80
Purchase #7	$15.92	8.718%	$17.3079	$17.31	$17.30	$17.30
7 purchase totals =	$663.71		$699.4557	$699.47	$699.40	$699.60