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	$56.85	8.466%	$61.6629	$61.66	$61.65	$61.70
Purchase #2	$232.46	7.405%	$249.6737	$249.67	$249.65	$249.70
Purchase #3	$80.73	12.387%	$90.73	$90.73	$90.75	$90.70
Purchase #4	$72.43	13.807%	$82.4304	$82.43	$82.45	$82.40
Purchase #5	$232.30	10.581%	$256.8797	$256.88	$256.90	$256.90
Purchase #6	$118.82	9.743%	$130.3966	$130.40	$130.40	$130.40
Purchase #7	$83.43	11.831%	$93.3006	$93.30	$93.30	$93.30
7 purchase totals =	$877.02		$965.0739	$965.07	$965.10	$965.10