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	$153.53	12.519%	$172.7504	$172.75	$172.75	$172.80
Purchase #2	$106.88	8.570%	$116.0396	$116.04	$116.05	$116.00
Purchase #3	$34.64	10.816%	$38.3867	$38.39	$38.40	$38.40
Purchase #4	$36.52	10.117%	$40.2147	$40.21	$40.20	$40.20
Purchase #5	$213.88	4.524%	$223.5559	$223.56	$223.55	$223.60
Purchase #6	$61.34	11.478%	$68.3806	$68.38	$68.40	$68.40
Purchase #7	$134.78	3.232%	$139.1361	$139.14	$139.15	$139.10
7 purchase totals =	$741.57		$798.4640	$798.47	$798.50	$798.50