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	$79.53	7.145%	$85.2124	$85.21	$85.20	$85.20
Purchase #2	$23.50	13.803%	$26.7437	$26.74	$26.75	$26.70
Purchase #3	$93.66	5.776%	$99.0698	$99.07	$99.05	$99.10
Purchase #4	$160.46	11.487%	$178.892	$178.89	$178.90	$178.90
Purchase #5	$186.38	12.647%	$209.9515	$209.95	$209.95	$210.00
Purchase #6	$185.83	12.178%	$208.4604	$208.46	$208.45	$208.50
Purchase #7	$174.66	11.426%	$194.6167	$194.62	$194.60	$194.60
7 purchase totals =	$904.02		$1,002.9465	$1,002.94	$1,002.90	$1,003.00