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	$203.61	4.820%	$213.424	$213.42	$213.40	$213.40
Purchase #2	$244.75	13.683%	$278.2391	$278.24	$278.25	$278.20
Purchase #3	$228.98	3.807%	$237.6973	$237.70	$237.70	$237.70
Purchase #4	$28.60	12.130%	$32.0692	$32.07	$32.05	$32.10
Purchase #5	$157.25	3.345%	$162.51	$162.51	$162.50	$162.50
Purchase #6	$29.47	11.485%	$32.8546	$32.85	$32.85	$32.90
Purchase #7	$131.72	9.117%	$143.7289	$143.73	$143.75	$143.70
7 purchase totals =	$1,024.38		$1,100.5231	$1,100.52	$1,100.50	$1,100.50