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	$67.33	7.644%	$72.4767	$72.48	$72.50	$72.50
Purchase #2	$86.53	4.517%	$90.4386	$90.44	$90.45	$90.40
Purchase #3	$145.78	8.308%	$157.8914	$157.89	$157.90	$157.90
Purchase #4	$216.41	4.161%	$225.4148	$225.41	$225.40	$225.40
Purchase #5	$99.80	12.118%	$111.8938	$111.89	$111.90	$111.90
Purchase #6	$121.45	4.490%	$126.9031	$126.90	$126.90	$126.90
Purchase #7	$228.37	7.820%	$246.2285	$246.23	$246.25	$246.20
7 purchase totals =	$965.67		$1,031.2469	$1,031.24	$1,031.30	$1,031.20