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	$237.56	5.303%	$250.1578	$250.16	$250.15	$250.20
Purchase #2	$62.75	13.272%	$71.0782	$71.08	$71.10	$71.10
Purchase #3	$142.62	4.188%	$148.5929	$148.59	$148.60	$148.60
Purchase #4	$26.99	10.694%	$29.8763	$29.88	$29.90	$29.90
Purchase #5	$211.38	9.597%	$231.6661	$231.67	$231.65	$231.70
Purchase #6	$144.82	6.806%	$154.6764	$154.68	$154.70	$154.70
Purchase #7	$104.80	6.306%	$111.4087	$111.41	$111.40	$111.40
7 purchase totals =	$930.92		$997.4564	$997.47	$997.50	$997.60