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	$250.73	10.293%	$276.5376	$276.54	$276.55	$276.50
Purchase #2	$189.55	6.123%	$201.1561	$201.16	$201.15	$201.20
Purchase #3	$30.60	8.797%	$33.2919	$33.29	$33.30	$33.30
Purchase #4	$126.49	4.733%	$132.4768	$132.48	$132.50	$132.50
Purchase #5	$152.54	10.346%	$168.3218	$168.32	$168.30	$168.30
Purchase #6	$72.31	13.509%	$82.0784	$82.08	$82.10	$82.10
Purchase #7	$150.86	6.554%	$160.7474	$160.75	$160.75	$160.70
7 purchase totals =	$973.08		$1,054.6100	$1,054.62	$1,054.65	$1,054.60