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	$21.47	11.850%	$24.0142	$24.01	$24.00	$24.00
Purchase #2	$9.93	9.333%	$10.8568	$10.86	$10.85	$10.90
Purchase #3	$78.32	11.518%	$87.3409	$87.34	$87.35	$87.30
Purchase #4	$39.81	6.333%	$42.3312	$42.33	$42.35	$42.30
Purchase #5	$233.65	9.765%	$256.4659	$256.47	$256.45	$256.50
Purchase #6	$140.58	5.642%	$148.5115	$148.51	$148.50	$148.50
Purchase #7	$186.67	13.753%	$212.3427	$212.34	$212.35	$212.30
7 purchase totals =	$710.43		$781.8632	$781.86	$781.85	$781.80