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	$59.51	13.255%	$67.3981	$67.40	$67.40	$67.40
Purchase #2	$17.35	5.762%	$18.3497	$18.35	$18.35	$18.30
Purchase #3	$65.71	9.690%	$72.0773	$72.08	$72.10	$72.10
Purchase #4	$186.68	12.445%	$209.9123	$209.91	$209.90	$209.90
Purchase #5	$90.44	3.192%	$93.3268	$93.33	$93.35	$93.30
Purchase #6	$180.70	8.642%	$196.3161	$196.32	$196.30	$196.30
Purchase #7	$235.69	10.342%	$260.0651	$260.07	$260.05	$260.10
7 purchase totals =	$836.08		$917.4454	$917.46	$917.45	$917.40