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	$71.34	4.617%	$74.6338	$74.63	$74.65	$74.60
Purchase #2	$30.80	7.167%	$33.0074	$33.01	$33.00	$33.00
Purchase #3	$162.57	10.394%	$179.4675	$179.47	$179.45	$179.50
Purchase #4	$204.98	8.555%	$222.516	$222.52	$222.50	$222.50
Purchase #5	$7.32	6.836%	$7.8204	$7.82	$7.80	$7.80
Purchase #6	$77.77	11.561%	$86.761	$86.76	$86.75	$86.80
Purchase #7	$232.85	4.460%	$243.2351	$243.24	$243.25	$243.20
7 purchase totals =	$787.63		$847.4412	$847.45	$847.40	$847.40