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	$211.28	13.336%	$239.4563	$239.46	$239.45	$239.50
Purchase #2	$57.40	9.255%	$62.7124	$62.71	$62.70	$62.70
Purchase #3	$187.62	11.352%	$208.9186	$208.92	$208.90	$208.90
Purchase #4	$100.70	10.454%	$111.2272	$111.23	$111.25	$111.20
Purchase #5	$76.66	8.795%	$83.4022	$83.40	$83.40	$83.40
Purchase #6	$158.76	4.440%	$165.8089	$165.81	$165.80	$165.80
Purchase #7	$151.74	12.562%	$170.8016	$170.80	$170.80	$170.80
7 purchase totals =	$944.16		$1,042.3272	$1,042.33	$1,042.30	$1,042.30