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	$222.72	11.265%	$247.8094	$247.81	$247.80	$247.80
Purchase #2	$89.61	10.295%	$98.8353	$98.84	$98.85	$98.80
Purchase #3	$56.67	10.126%	$62.4084	$62.41	$62.40	$62.40
Purchase #4	$145.60	11.583%	$162.4648	$162.46	$162.45	$162.50
Purchase #5	$217.49	13.813%	$247.5319	$247.53	$247.55	$247.50
Purchase #6	$38.69	10.686%	$42.8244	$42.82	$42.80	$42.80
Purchase #7	$100.38	8.767%	$109.1803	$109.18	$109.20	$109.20
7 purchase totals =	$871.16		$971.0545	$971.05	$971.05	$971.00