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	$96.83	9.117%	$105.658	$105.66	$105.65	$105.70
Purchase #2	$104.34	11.402%	$116.2368	$116.24	$116.25	$116.20
Purchase #3	$46.52	8.723%	$50.5779	$50.58	$50.60	$50.60
Purchase #4	$34.96	8.294%	$37.8596	$37.86	$37.85	$37.90
Purchase #5	$185.25	7.237%	$198.6565	$198.66	$198.65	$198.70
Purchase #6	$25.50	7.254%	$27.3498	$27.35	$27.35	$27.30
Purchase #7	$197.85	12.656%	$222.8899	$222.89	$222.90	$222.90
7 purchase totals =	$691.25		$759.2285	$759.24	$759.25	$759.30