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	$204.27	10.530%	$225.7796	$225.78	$225.80	$225.80
Purchase #2	$236.33	6.686%	$252.131	$252.13	$252.15	$252.10
Purchase #3	$47.43	10.873%	$52.5871	$52.59	$52.60	$52.60
Purchase #4	$172.67	13.428%	$195.8561	$195.86	$195.85	$195.90
Purchase #5	$88.66	12.698%	$99.918	$99.92	$99.90	$99.90
Purchase #6	$222.32	7.474%	$238.9362	$238.94	$238.95	$238.90
Purchase #7	$51.42	12.460%	$57.8269	$57.83	$57.85	$57.80
7 purchase totals =	$1,023.10		$1,123.0349	$1,123.05	$1,123.10	$1,123.00