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	$112.99	12.298%	$126.8855	$126.89	$126.90	$126.90
Purchase #2	$214.63	9.310%	$234.6121	$234.61	$234.60	$234.60
Purchase #3	$105.87	5.446%	$111.6357	$111.64	$111.65	$111.60
Purchase #4	$6.67	7.456%	$7.1673	$7.17	$7.15	$7.20
Purchase #5	$128.41	5.403%	$135.348	$135.35	$135.35	$135.30
Purchase #6	$52.80	13.384%	$59.8668	$59.87	$59.85	$59.90
Purchase #7	$77.94	5.506%	$82.2314	$82.23	$82.25	$82.20
7 purchase totals =	$699.31		$757.7468	$757.76	$757.75	$757.70