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	$221.35	5.429%	$233.3671	$233.37	$233.35	$233.40
Purchase #2	$119.69	5.578%	$126.3663	$126.37	$126.35	$126.40
Purchase #3	$55.78	7.134%	$59.7593	$59.76	$59.75	$59.80
Purchase #4	$250.36	12.223%	$280.9615	$280.96	$280.95	$281.00
Purchase #5	$170.84	12.198%	$191.6791	$191.68	$191.70	$191.70
Purchase #6	$114.97	8.415%	$124.6447	$124.64	$124.65	$124.60
Purchase #7	$139.29	13.512%	$158.1109	$158.11	$158.10	$158.10
7 purchase totals =	$1,072.28		$1,174.8889	$1,174.89	$1,174.85	$1,175.00