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	$186.57	8.118%	$201.7158	$201.72	$201.70	$201.70
Purchase #2	$180.32	11.389%	$200.8566	$200.86	$200.85	$200.90
Purchase #3	$40.70	10.293%	$44.8893	$44.89	$44.90	$44.90
Purchase #4	$87.83	4.140%	$91.4662	$91.47	$91.45	$91.50
Purchase #5	$217.62	4.560%	$227.5435	$227.54	$227.55	$227.50
Purchase #6	$34.46	9.835%	$37.8491	$37.85	$37.85	$37.80
Purchase #7	$190.26	3.621%	$197.1493	$197.15	$197.15	$197.10
7 purchase totals =	$937.76		$1,001.4698	$1,001.48	$1,001.45	$1,001.40