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	$47.69	7.758%	$51.3898	$51.39	$51.40	$51.40
Purchase #2	$197.30	13.302%	$223.5448	$223.54	$223.55	$223.50
Purchase #3	$237.41	11.325%	$264.2967	$264.30	$264.30	$264.30
Purchase #4	$174.85	4.692%	$183.054	$183.05	$183.05	$183.10
Purchase #5	$229.45	11.680%	$256.2498	$256.25	$256.25	$256.20
Purchase #6	$250.83	9.340%	$274.2575	$274.26	$274.25	$274.30
Purchase #7	$151.84	4.806%	$159.1374	$159.14	$159.15	$159.10
7 purchase totals =	$1,289.37		$1,411.9300	$1,411.93	$1,411.95	$1,411.90