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	$105.30	7.733%	$113.4428	$113.44	$113.45	$113.40
Purchase #2	$237.29	13.846%	$270.1452	$270.15	$270.15	$270.10
Purchase #3	$67.79	6.839%	$72.4262	$72.43	$72.45	$72.40
Purchase #4	$213.69	13.516%	$242.5723	$242.57	$242.55	$242.60
Purchase #5	$160.48	7.626%	$172.7182	$172.72	$172.70	$172.70
Purchase #6	$164.76	6.630%	$175.6836	$175.68	$175.70	$175.70
Purchase #7	$247.49	10.757%	$274.1125	$274.11	$274.10	$274.10
7 purchase totals =	$1,196.80		$1,321.1008	$1,321.10	$1,321.10	$1,321.00