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	$156.85	9.344%	$171.5061	$171.51	$171.50	$171.50
Purchase #2	$217.56	10.811%	$241.0804	$241.08	$241.10	$241.10
Purchase #3	$37.54	13.741%	$42.6984	$42.70	$42.70	$42.70
Purchase #4	$55.97	8.104%	$60.5058	$60.51	$60.50	$60.50
Purchase #5	$200.85	13.153%	$227.2678	$227.27	$227.25	$227.30
Purchase #6	$63.41	11.291%	$70.5696	$70.57	$70.55	$70.60
Purchase #7	$211.67	8.510%	$229.6831	$229.68	$229.70	$229.70
7 purchase totals =	$943.85		$1,043.3112	$1,043.32	$1,043.30	$1,043.40