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	$199.57	7.592%	$214.7214	$214.72	$214.70	$214.70
Purchase #2	$234.81	3.345%	$242.6644	$242.66	$242.65	$242.70
Purchase #3	$128.50	12.546%	$144.6216	$144.62	$144.60	$144.60
Purchase #4	$16.41	10.611%	$18.1513	$18.15	$18.15	$18.20
Purchase #5	$40.49	4.355%	$42.2533	$42.25	$42.25	$42.30
Purchase #6	$172.48	7.421%	$185.2797	$185.28	$185.30	$185.30
Purchase #7	$60.90	7.588%	$65.5211	$65.52	$65.50	$65.50
7 purchase totals =	$853.16		$913.2128	$913.20	$913.15	$913.30