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	$116.86	12.778%	$131.7924	$131.79	$131.80	$131.80
Purchase #2	$133.46	11.107%	$148.2834	$148.28	$148.30	$148.30
Purchase #3	$59.64	3.404%	$61.6701	$61.67	$61.65	$61.70
Purchase #4	$9.65	6.527%	$10.2799	$10.28	$10.30	$10.30
Purchase #5	$224.32	10.481%	$247.831	$247.83	$247.85	$247.80
Purchase #6	$192.39	13.509%	$218.38	$218.38	$218.40	$218.40
Purchase #7	$109.94	5.410%	$115.8878	$115.89	$115.90	$115.90
7 purchase totals =	$846.26		$934.1246	$934.12	$934.20	$934.20