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	$124.93	13.733%	$142.0866	$142.09	$142.10	$142.10
Purchase #2	$195.37	6.797%	$208.6493	$208.65	$208.65	$208.60
Purchase #3	$62.74	7.762%	$67.6099	$67.61	$67.60	$67.60
Purchase #4	$128.86	13.429%	$146.1646	$146.16	$146.15	$146.20
Purchase #5	$229.46	10.730%	$254.0811	$254.08	$254.10	$254.10
Purchase #6	$65.76	11.770%	$73.5	$73.50	$73.50	$73.50
Purchase #7	$173.47	12.150%	$194.5466	$194.55	$194.55	$194.50
7 purchase totals =	$980.59		$1,086.6381	$1,086.64	$1,086.65	$1,086.60