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	$139.82	10.600%	$154.6409	$154.64	$154.65	$154.60
Purchase #2	$125.43	12.449%	$141.0448	$141.04	$141.05	$141.00
Purchase #3	$50.67	9.118%	$55.2901	$55.29	$55.30	$55.30
Purchase #4	$50.98	7.873%	$54.9937	$54.99	$55.00	$55.00
Purchase #5	$133.75	13.650%	$152.0069	$152.01	$152.00	$152.00
Purchase #6	$40.66	4.770%	$42.5995	$42.60	$42.60	$42.60
Purchase #7	$167.83	8.519%	$182.1274	$182.13	$182.15	$182.10
7 purchase totals =	$709.14		$782.7033	$782.70	$782.75	$782.60