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	$159.31	10.197%	$175.5548	$175.55	$175.55	$175.60
Purchase #2	$143.32	8.251%	$155.1453	$155.15	$155.15	$155.10
Purchase #3	$35.49	13.463%	$40.268	$40.27	$40.25	$40.30
Purchase #4	$181.35	10.788%	$200.914	$200.91	$200.90	$200.90
Purchase #5	$244.97	11.497%	$273.1342	$273.13	$273.15	$273.10
Purchase #6	$200.90	7.275%	$215.5155	$215.52	$215.50	$215.50
Purchase #7	$200.58	11.863%	$224.3748	$224.37	$224.35	$224.40
7 purchase totals =	$1,165.92		$1,284.9066	$1,284.90	$1,284.85	$1,284.90