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	$120.37	3.791%	$124.9332	$124.93	$124.95	$124.90
Purchase #2	$111.61	12.638%	$125.7153	$125.72	$125.70	$125.70
Purchase #3	$11.76	8.539%	$12.7642	$12.76	$12.75	$12.80
Purchase #4	$94.38	6.461%	$100.4779	$100.48	$100.50	$100.50
Purchase #5	$182.60	9.231%	$199.4558	$199.46	$199.45	$199.50
Purchase #6	$30.89	3.222%	$31.8853	$31.89	$31.90	$31.90
Purchase #7	$230.65	3.618%	$238.9949	$238.99	$239.00	$239.00
7 purchase totals =	$782.26		$834.2266	$834.23	$834.25	$834.30