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	$235.79	6.306%	$250.6589	$250.66	$250.65	$250.70
Purchase #2	$151.93	10.797%	$168.3339	$168.33	$168.35	$168.30
Purchase #3	$19.53	10.644%	$21.6088	$21.61	$21.60	$21.60
Purchase #4	$101.34	10.133%	$111.6088	$111.61	$111.60	$111.60
Purchase #5	$208.42	11.253%	$231.8735	$231.87	$231.85	$231.90
Purchase #6	$224.69	4.226%	$234.1854	$234.19	$234.20	$234.20
Purchase #7	$42.86	8.132%	$46.3454	$46.35	$46.35	$46.30
7 purchase totals =	$984.56		$1,064.6147	$1,064.62	$1,064.60	$1,064.60