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	$91.72	7.810%	$98.8833	$98.88	$98.90	$98.90
Purchase #2	$69.71	10.624%	$77.116	$77.12	$77.10	$77.10
Purchase #3	$200.78	5.804%	$212.4333	$212.43	$212.45	$212.40
Purchase #4	$185.65	4.406%	$193.8297	$193.83	$193.85	$193.80
Purchase #5	$211.71	7.644%	$227.8931	$227.89	$227.90	$227.90
Purchase #6	$238.88	12.644%	$269.084	$269.08	$269.10	$269.10
Purchase #7	$62.67	6.551%	$66.7755	$66.78	$66.80	$66.80
7 purchase totals =	$1,061.12		$1,146.0149	$1,146.01	$1,146.10	$1,146.00