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	$243.58	5.283%	$256.4483	$256.45	$256.45	$256.40
Purchase #2	$54.82	11.702%	$61.235	$61.24	$61.25	$61.20
Purchase #3	$65.43	10.244%	$72.1326	$72.13	$72.15	$72.10
Purchase #4	$65.65	5.171%	$69.0448	$69.04	$69.05	$69.00
Purchase #5	$138.60	12.236%	$155.5591	$155.56	$155.55	$155.60
Purchase #6	$58.55	11.259%	$65.1421	$65.14	$65.15	$65.10
Purchase #7	$237.46	4.369%	$247.8346	$247.83	$247.85	$247.80
7 purchase totals =	$864.09		$927.3965	$927.39	$927.45	$927.20