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	$235.48	12.632%	$265.2258	$265.23	$265.25	$265.20
Purchase #2	$64.82	9.682%	$71.0959	$71.10	$71.10	$71.10
Purchase #3	$45.89	4.387%	$47.9032	$47.90	$47.90	$47.90
Purchase #4	$16.87	7.742%	$18.1761	$18.18	$18.20	$18.20
Purchase #5	$33.35	12.393%	$37.4831	$37.48	$37.50	$37.50
Purchase #6	$154.80	13.257%	$175.3218	$175.32	$175.30	$175.30
Purchase #7	$101.38	8.365%	$109.8604	$109.86	$109.85	$109.90
7 purchase totals =	$652.59		$725.0663	$725.07	$725.10	$725.10