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	$38.66	7.393%	$41.5181	$41.52	$41.50	$41.50
Purchase #2	$81.88	12.395%	$92.029	$92.03	$92.05	$92.00
Purchase #3	$232.50	11.340%	$258.8655	$258.87	$258.85	$258.90
Purchase #4	$224.51	9.560%	$245.9732	$245.97	$245.95	$246.00
Purchase #5	$81.40	9.752%	$89.3381	$89.34	$89.35	$89.30
Purchase #6	$139.38	3.681%	$144.5106	$144.51	$144.50	$144.50
Purchase #7	$12.76	8.657%	$13.8646	$13.86	$13.85	$13.90
7 purchase totals =	$811.09		$886.0991	$886.10	$886.05	$886.10