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	$172.48	10.256%	$190.1695	$190.17	$190.15	$190.20
Purchase #2	$140.32	12.781%	$158.2543	$158.25	$158.25	$158.30
Purchase #3	$42.36	12.565%	$47.6825	$47.68	$47.70	$47.70
Purchase #4	$168.26	6.691%	$179.5183	$179.52	$179.50	$179.50
Purchase #5	$24.79	3.192%	$25.5813	$25.58	$25.60	$25.60
Purchase #6	$155.55	8.228%	$168.3487	$168.35	$168.35	$168.30
Purchase #7	$234.48	10.339%	$258.7229	$258.72	$258.70	$258.70
7 purchase totals =	$938.24		$1,028.2775	$1,028.27	$1,028.25	$1,028.30