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	$113.25	12.857%	$127.8106	$127.81	$127.80	$127.80
Purchase #2	$209.25	3.348%	$216.2557	$216.26	$216.25	$216.30
Purchase #3	$198.35	12.605%	$223.352	$223.35	$223.35	$223.40
Purchase #4	$105.55	10.115%	$116.2264	$116.23	$116.25	$116.20
Purchase #5	$44.70	4.521%	$46.7209	$46.72	$46.70	$46.70
Purchase #6	$35.67	6.363%	$37.9397	$37.94	$37.95	$37.90
Purchase #7	$160.53	11.272%	$178.6249	$178.62	$178.60	$178.60
7 purchase totals =	$867.30		$946.9302	$946.93	$946.90	$946.90