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	$125.98	3.498%	$130.3868	$130.39	$130.40	$130.40
Purchase #2	$161.99	11.638%	$180.8424	$180.84	$180.85	$180.80
Purchase #3	$100.26	10.848%	$111.1362	$111.14	$111.15	$111.10
Purchase #4	$120.33	9.605%	$131.8877	$131.89	$131.90	$131.90
Purchase #5	$196.72	12.374%	$221.0621	$221.06	$221.05	$221.10
Purchase #6	$140.93	6.766%	$150.4653	$150.47	$150.45	$150.50
Purchase #7	$213.81	9.325%	$233.7478	$233.75	$233.75	$233.70
7 purchase totals =	$1,060.02		$1,159.5283	$1,159.54	$1,159.55	$1,159.50