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	$244.65	4.372%	$255.3461	$255.35	$255.35	$255.30
Purchase #2	$172.55	13.641%	$196.0875	$196.09	$196.10	$196.10
Purchase #3	$193.85	8.274%	$209.8891	$209.89	$209.90	$209.90
Purchase #4	$249.73	8.727%	$271.5239	$271.52	$271.50	$271.50
Purchase #5	$92.80	13.778%	$105.586	$105.59	$105.60	$105.60
Purchase #6	$120.52	6.812%	$128.7298	$128.73	$128.75	$128.70
Purchase #7	$211.90	10.490%	$234.1283	$234.13	$234.15	$234.10
7 purchase totals =	$1,286.00		$1,401.2907	$1,401.30	$1,401.35	$1,401.20