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	$57.46	6.866%	$61.4052	$61.41	$61.40	$61.40
Purchase #2	$42.81	5.115%	$44.9997	$45.00	$45.00	$45.00
Purchase #3	$89.31	8.773%	$97.1452	$97.15	$97.15	$97.10
Purchase #4	$117.34	11.341%	$130.6475	$130.65	$130.65	$130.60
Purchase #5	$184.71	8.164%	$199.7897	$199.79	$199.80	$199.80
Purchase #6	$240.46	6.804%	$256.8209	$256.82	$256.80	$256.80
Purchase #7	$85.44	5.491%	$90.1315	$90.13	$90.15	$90.10
7 purchase totals =	$817.53		$880.9397	$880.95	$880.95	$880.80