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	$119.47	11.291%	$132.9594	$132.96	$132.95	$133.00
Purchase #2	$140.72	11.323%	$156.6537	$156.65	$156.65	$156.70
Purchase #3	$34.69	8.692%	$37.7053	$37.71	$37.70	$37.70
Purchase #4	$114.43	5.300%	$120.4948	$120.49	$120.50	$120.50
Purchase #5	$101.52	13.166%	$114.8861	$114.89	$114.90	$114.90
Purchase #6	$110.43	12.230%	$123.9356	$123.94	$123.95	$123.90
Purchase #7	$78.98	5.205%	$83.0909	$83.09	$83.10	$83.10
7 purchase totals =	$700.24		$769.7258	$769.73	$769.75	$769.80