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	$111.76	11.479%	$124.5889	$124.59	$124.60	$124.60
Purchase #2	$185.35	3.348%	$191.5555	$191.56	$191.55	$191.60
Purchase #3	$196.62	12.412%	$221.0245	$221.02	$221.00	$221.00
Purchase #4	$94.70	12.578%	$106.6114	$106.61	$106.60	$106.60
Purchase #5	$205.83	13.842%	$234.321	$234.32	$234.30	$234.30
Purchase #6	$34.93	12.789%	$39.3972	$39.40	$39.40	$39.40
Purchase #7	$196.74	13.582%	$223.4612	$223.46	$223.45	$223.50
7 purchase totals =	$1,025.93		$1,140.9597	$1,140.96	$1,140.90	$1,141.00