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	$244.52	12.346%	$274.7084	$274.71	$274.70	$274.70
Purchase #2	$187.47	6.857%	$200.3248	$200.32	$200.30	$200.30
Purchase #3	$224.35	9.129%	$244.8309	$244.83	$244.85	$244.80
Purchase #4	$181.32	10.603%	$200.5454	$200.55	$200.55	$200.50
Purchase #5	$155.55	10.452%	$171.8081	$171.81	$171.80	$171.80
Purchase #6	$83.30	13.377%	$94.443	$94.44	$94.45	$94.40
Purchase #7	$24.66	3.557%	$25.5372	$25.54	$25.55	$25.50
7 purchase totals =	$1,101.17		$1,212.1978	$1,212.20	$1,212.20	$1,212.00