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	$74.31	11.238%	$82.661	$82.66	$82.65	$82.70
Purchase #2	$174.96	9.455%	$191.5025	$191.50	$191.50	$191.50
Purchase #3	$78.85	8.231%	$85.3401	$85.34	$85.35	$85.30
Purchase #4	$116.51	5.431%	$122.8377	$122.84	$122.85	$122.80
Purchase #5	$137.85	11.587%	$153.8227	$153.82	$153.80	$153.80
Purchase #6	$225.41	9.481%	$246.7811	$246.78	$246.80	$246.80
Purchase #7	$107.73	11.566%	$120.1901	$120.19	$120.20	$120.20
7 purchase totals =	$915.62		$1,003.1352	$1,003.13	$1,003.15	$1,003.10