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	$116.72	6.350%	$124.1317	$124.13	$124.15	$124.10
Purchase #2	$182.91	9.605%	$200.4785	$200.48	$200.50	$200.50
Purchase #3	$202.52	11.107%	$225.0139	$225.01	$225.00	$225.00
Purchase #4	$140.80	8.298%	$152.4836	$152.48	$152.50	$152.50
Purchase #5	$119.83	12.128%	$134.363	$134.36	$134.35	$134.40
Purchase #6	$77.71	10.312%	$85.7235	$85.72	$85.70	$85.70
Purchase #7	$42.77	6.859%	$45.7036	$45.70	$45.70	$45.70
7 purchase totals =	$883.26		$967.8978	$967.88	$967.90	$967.90