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	$129.77	11.761%	$145.0322	$145.03	$145.05	$145.00
Purchase #2	$227.47	7.753%	$245.1057	$245.11	$245.10	$245.10
Purchase #3	$243.75	3.847%	$253.1271	$253.13	$253.15	$253.10
Purchase #4	$150.68	13.145%	$170.4869	$170.49	$170.50	$170.50
Purchase #5	$64.70	7.315%	$69.4328	$69.43	$69.45	$69.40
Purchase #6	$38.80	10.255%	$42.7789	$42.78	$42.80	$42.80
Purchase #7	$126.55	4.198%	$131.8626	$131.86	$131.85	$131.90
7 purchase totals =	$981.72		$1,057.8262	$1,057.83	$1,057.90	$1,057.80