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	$249.89	7.842%	$269.4864	$269.49	$269.50	$269.50
Purchase #2	$132.67	3.337%	$137.0972	$137.10	$137.10	$137.10
Purchase #3	$107.96	5.182%	$113.5545	$113.55	$113.55	$113.60
Purchase #4	$220.30	5.184%	$231.7204	$231.72	$231.70	$231.70
Purchase #5	$212.90	4.338%	$222.1356	$222.14	$222.15	$222.10
Purchase #6	$150.73	7.173%	$161.5419	$161.54	$161.55	$161.50
Purchase #7	$248.66	6.810%	$265.5937	$265.59	$265.60	$265.60
7 purchase totals =	$1,323.11		$1,401.1297	$1,401.13	$1,401.15	$1,401.10