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	$133.74	13.386%	$151.6424	$151.64	$151.65	$151.60
Purchase #2	$129.47	3.458%	$133.9471	$133.95	$133.95	$133.90
Purchase #3	$33.73	6.460%	$35.909	$35.91	$35.90	$35.90
Purchase #4	$16.89	8.315%	$18.2944	$18.29	$18.30	$18.30
Purchase #5	$50.62	13.795%	$57.603	$57.60	$57.60	$57.60
Purchase #6	$64.86	4.706%	$67.9123	$67.91	$67.90	$67.90
Purchase #7	$99.65	3.782%	$103.4188	$103.42	$103.40	$103.40
7 purchase totals =	$528.96		$568.7270	$568.72	$568.70	$568.60