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	$226.94	10.803%	$251.4563	$251.46	$251.45	$251.50
Purchase #2	$145.39	8.154%	$157.2451	$157.25	$157.25	$157.20
Purchase #3	$45.86	9.358%	$50.1516	$50.15	$50.15	$50.20
Purchase #4	$141.54	7.654%	$152.3735	$152.37	$152.35	$152.40
Purchase #5	$45.66	11.459%	$50.8922	$50.89	$50.90	$50.90
Purchase #6	$132.42	6.874%	$141.5226	$141.52	$141.50	$141.50
Purchase #7	$222.99	8.400%	$241.7212	$241.72	$241.70	$241.70
7 purchase totals =	$960.80		$1,045.3625	$1,045.36	$1,045.30	$1,045.40