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	$155.64	3.282%	$160.7481	$160.75	$160.75	$160.70
Purchase #2	$55.60	7.596%	$59.8234	$59.82	$59.80	$59.80
Purchase #3	$8.45	13.687%	$9.6066	$9.61	$9.60	$9.60
Purchase #4	$221.80	7.686%	$238.8475	$238.85	$238.85	$238.80
Purchase #5	$212.57	10.495%	$234.8792	$234.88	$234.90	$234.90
Purchase #6	$199.88	11.803%	$223.4718	$223.47	$223.45	$223.50
Purchase #7	$94.95	9.186%	$103.6721	$103.67	$103.65	$103.70
7 purchase totals =	$948.89		$1,031.0487	$1,031.05	$1,031.00	$1,031.00