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	$151.38	13.455%	$171.7482	$171.75	$171.75	$171.70
Purchase #2	$208.42	4.347%	$217.48	$217.48	$217.50	$217.50
Purchase #3	$182.83	11.694%	$204.2101	$204.21	$204.20	$204.20
Purchase #4	$43.36	3.145%	$44.7237	$44.72	$44.70	$44.70
Purchase #5	$202.78	10.276%	$223.6177	$223.62	$223.60	$223.60
Purchase #6	$127.29	8.503%	$138.1135	$138.11	$138.10	$138.10
Purchase #7	$58.78	4.772%	$61.585	$61.59	$61.60	$61.60
7 purchase totals =	$974.84		$1,061.4782	$1,061.48	$1,061.45	$1,061.40