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	$120.61	4.286%	$125.7793	$125.78	$125.80	$125.80
Purchase #2	$139.92	6.810%	$149.4486	$149.45	$149.45	$149.40
Purchase #3	$178.33	10.352%	$196.7907	$196.79	$196.80	$196.80
Purchase #4	$43.72	9.383%	$47.8222	$47.82	$47.80	$47.80
Purchase #5	$40.43	6.422%	$43.0264	$43.03	$43.05	$43.00
Purchase #6	$13.34	8.340%	$14.4526	$14.45	$14.45	$14.50
Purchase #7	$145.48	10.675%	$161.01	$161.01	$161.00	$161.00
7 purchase totals =	$681.83		$738.3298	$738.33	$738.35	$738.30