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	$125.62	12.178%	$140.918	$140.92	$140.90	$140.90
Purchase #2	$30.44	10.281%	$33.5695	$33.57	$33.55	$33.60
Purchase #3	$96.98	5.570%	$102.3818	$102.38	$102.40	$102.40
Purchase #4	$99.61	11.779%	$111.3431	$111.34	$111.35	$111.30
Purchase #5	$237.67	7.473%	$255.4311	$255.43	$255.45	$255.40
Purchase #6	$153.82	12.118%	$172.4599	$172.46	$172.45	$172.50
Purchase #7	$22.53	13.806%	$25.6405	$25.64	$25.65	$25.60
7 purchase totals =	$766.67		$841.7439	$841.74	$841.75	$841.70