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	$205.35	12.536%	$231.0927	$231.09	$231.10	$231.10
Purchase #2	$29.54	13.506%	$33.5297	$33.53	$33.55	$33.50
Purchase #3	$100.85	4.796%	$105.6868	$105.69	$105.70	$105.70
Purchase #4	$38.96	5.754%	$41.2018	$41.20	$41.20	$41.20
Purchase #5	$101.79	10.173%	$112.1451	$112.15	$112.15	$112.10
Purchase #6	$111.76	11.682%	$124.8158	$124.82	$124.80	$124.80
Purchase #7	$100.41	11.735%	$112.1931	$112.19	$112.20	$112.20
7 purchase totals =	$688.66		$760.6650	$760.67	$760.70	$760.60