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	$117.45	6.364%	$124.9245	$124.92	$124.90	$124.90
Purchase #2	$66.48	13.718%	$75.5997	$75.60	$75.60	$75.60
Purchase #3	$39.38	4.719%	$41.2383	$41.24	$41.25	$41.20
Purchase #4	$33.72	7.567%	$36.2716	$36.27	$36.25	$36.30
Purchase #5	$225.43	13.353%	$255.5317	$255.53	$255.55	$255.50
Purchase #6	$111.35	10.624%	$123.1798	$123.18	$123.20	$123.20
Purchase #7	$29.70	9.561%	$32.5396	$32.54	$32.55	$32.50
7 purchase totals =	$623.51		$689.2852	$689.28	$689.30	$689.20