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	$223.32	12.113%	$250.3708	$250.37	$250.35	$250.40
Purchase #2	$243.56	11.833%	$272.3805	$272.38	$272.40	$272.40
Purchase #3	$39.93	5.351%	$42.0667	$42.07	$42.05	$42.10
Purchase #4	$231.68	3.499%	$239.7865	$239.79	$239.80	$239.80
Purchase #5	$43.32	5.276%	$45.6056	$45.61	$45.60	$45.60
Purchase #6	$129.37	5.496%	$136.4802	$136.48	$136.50	$136.50
Purchase #7	$241.30	13.735%	$274.4426	$274.44	$274.45	$274.40
7 purchase totals =	$1,152.48		$1,261.1329	$1,261.14	$1,261.15	$1,261.20