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	$116.27	5.447%	$122.6032	$122.60	$122.60	$122.60
Purchase #2	$19.89	3.374%	$20.5611	$20.56	$20.55	$20.60
Purchase #3	$88.62	12.770%	$99.9368	$99.94	$99.95	$99.90
Purchase #4	$119.51	4.149%	$124.4685	$124.47	$124.45	$124.50
Purchase #5	$52.73	10.835%	$58.4433	$58.44	$58.45	$58.40
Purchase #6	$24.84	4.114%	$25.8619	$25.86	$25.85	$25.90
Purchase #7	$18.80	8.861%	$20.4659	$20.47	$20.45	$20.50
7 purchase totals =	$440.66		$472.3407	$472.34	$472.30	$472.40