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	$247.56	3.800%	$256.9673	$256.97	$256.95	$257.00
Purchase #2	$247.93	9.486%	$271.4486	$271.45	$271.45	$271.40
Purchase #3	$31.82	10.760%	$35.2438	$35.24	$35.25	$35.20
Purchase #4	$166.76	6.801%	$178.1013	$178.10	$178.10	$178.10
Purchase #5	$136.56	5.130%	$143.5655	$143.57	$143.55	$143.60
Purchase #6	$140.59	5.634%	$148.5108	$148.51	$148.50	$148.50
Purchase #7	$159.86	4.385%	$166.8699	$166.87	$166.85	$166.90
7 purchase totals =	$1,131.08		$1,200.7072	$1,200.71	$1,200.65	$1,200.70