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	$242.29	8.736%	$263.4565	$263.46	$263.45	$263.50
Purchase #2	$83.32	11.570%	$92.9601	$92.96	$92.95	$93.00
Purchase #3	$64.27	11.846%	$71.8834	$71.88	$71.90	$71.90
Purchase #4	$16.84	11.850%	$18.8355	$18.84	$18.85	$18.80
Purchase #5	$56.70	5.681%	$59.9211	$59.92	$59.90	$59.90
Purchase #6	$40.69	13.166%	$46.0472	$46.05	$46.05	$46.00
Purchase #7	$161.90	4.126%	$168.58	$168.58	$168.60	$168.60
7 purchase totals =	$666.01		$721.6838	$721.69	$721.70	$721.70