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	$59.84	6.162%	$63.5273	$63.53	$63.55	$63.50
Purchase #2	$40.50	13.428%	$45.9383	$45.94	$45.95	$45.90
Purchase #3	$189.25	3.737%	$196.3223	$196.32	$196.30	$196.30
Purchase #4	$112.65	10.241%	$124.1865	$124.19	$124.20	$124.20
Purchase #5	$241.51	12.446%	$271.5683	$271.57	$271.55	$271.60
Purchase #6	$221.92	11.334%	$247.0724	$247.07	$247.05	$247.10
Purchase #7	$86.31	6.438%	$91.8666	$91.87	$91.85	$91.90
7 purchase totals =	$951.98		$1,040.4817	$1,040.49	$1,040.45	$1,040.50