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	$59.65	4.733%	$62.4732	$62.47	$62.45	$62.50
Purchase #2	$35.82	8.765%	$38.9596	$38.96	$38.95	$39.00
Purchase #3	$215.38	6.480%	$229.3366	$229.34	$229.35	$229.30
Purchase #4	$127.41	13.816%	$145.013	$145.01	$145.00	$145.00
Purchase #5	$100.31	13.386%	$113.7375	$113.74	$113.75	$113.70
Purchase #6	$247.80	4.730%	$259.5209	$259.52	$259.50	$259.50
Purchase #7	$248.39	13.457%	$281.8158	$281.82	$281.80	$281.80
7 purchase totals =	$1,034.76		$1,130.8566	$1,130.86	$1,130.80	$1,130.80