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	$134.75	12.443%	$151.5169	$151.52	$151.50	$151.50
Purchase #2	$135.45	13.171%	$153.2901	$153.29	$153.30	$153.30
Purchase #3	$29.59	12.792%	$33.3752	$33.38	$33.40	$33.40
Purchase #4	$99.43	4.233%	$103.6389	$103.64	$103.65	$103.60
Purchase #5	$72.73	7.863%	$78.4488	$78.45	$78.45	$78.40
Purchase #6	$203.28	9.652%	$222.9006	$222.90	$222.90	$222.90
Purchase #7	$22.32	3.439%	$23.0876	$23.09	$23.10	$23.10
7 purchase totals =	$697.55		$766.2581	$766.27	$766.30	$766.20