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	$178.71	11.841%	$199.8711	$199.87	$199.85	$199.90
Purchase #2	$89.53	11.383%	$99.7212	$99.72	$99.70	$99.70
Purchase #3	$38.25	5.434%	$40.3285	$40.33	$40.35	$40.30
Purchase #4	$12.65	5.259%	$13.3153	$13.32	$13.30	$13.30
Purchase #5	$59.43	12.505%	$66.8617	$66.86	$66.85	$66.90
Purchase #6	$151.86	5.646%	$160.434	$160.43	$160.45	$160.40
Purchase #7	$152.95	3.711%	$158.626	$158.63	$158.65	$158.60
7 purchase totals =	$683.38		$739.1578	$739.16	$739.15	$739.10