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	$163.37	13.490%	$185.4086	$185.41	$185.40	$185.40
Purchase #2	$130.93	8.871%	$142.5448	$142.54	$142.55	$142.50
Purchase #3	$20.89	7.733%	$22.5054	$22.51	$22.50	$22.50
Purchase #4	$110.74	11.788%	$123.794	$123.79	$123.80	$123.80
Purchase #5	$244.83	4.461%	$255.7519	$255.75	$255.75	$255.80
Purchase #6	$161.51	12.114%	$181.0753	$181.08	$181.10	$181.10
Purchase #7	$190.82	9.756%	$209.4364	$209.44	$209.45	$209.40
7 purchase totals =	$1,023.09		$1,120.5164	$1,120.52	$1,120.55	$1,120.50