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	$172.78	13.590%	$196.2608	$196.26	$196.25	$196.30
Purchase #2	$97.38	8.767%	$105.9173	$105.92	$105.90	$105.90
Purchase #3	$126.31	8.334%	$136.8367	$136.84	$136.85	$136.80
Purchase #4	$32.33	7.485%	$34.7499	$34.75	$34.75	$34.70
Purchase #5	$207.32	6.811%	$221.4406	$221.44	$221.45	$221.40
Purchase #6	$182.30	13.325%	$206.5915	$206.59	$206.60	$206.60
Purchase #7	$72.30	8.827%	$78.6819	$78.68	$78.70	$78.70
7 purchase totals =	$890.72		$980.4787	$980.48	$980.50	$980.40