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	$145.55	3.133%	$150.1101	$150.11	$150.10	$150.10
Purchase #2	$190.91	4.809%	$200.0909	$200.09	$200.10	$200.10
Purchase #3	$6.90	6.278%	$7.3332	$7.33	$7.35	$7.30
Purchase #4	$108.72	3.680%	$112.7209	$112.72	$112.70	$112.70
Purchase #5	$31.95	3.235%	$32.9836	$32.98	$33.00	$33.00
Purchase #6	$244.90	10.707%	$271.1214	$271.12	$271.10	$271.10
Purchase #7	$131.66	5.361%	$138.7183	$138.72	$138.70	$138.70
7 purchase totals =	$860.59		$913.0784	$913.07	$913.05	$913.00