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	$169.92	12.393%	$190.9782	$190.98	$191.00	$191.00
Purchase #2	$139.77	8.425%	$151.5456	$151.55	$151.55	$151.50
Purchase #3	$50.26	13.186%	$56.8873	$56.89	$56.90	$56.90
Purchase #4	$132.26	13.827%	$150.5476	$150.55	$150.55	$150.50
Purchase #5	$116.77	3.344%	$120.6748	$120.67	$120.65	$120.70
Purchase #6	$201.95	6.318%	$214.7092	$214.71	$214.70	$214.70
Purchase #7	$169.86	6.861%	$181.5141	$181.51	$181.50	$181.50
7 purchase totals =	$980.79		$1,066.8568	$1,066.86	$1,066.85	$1,066.80