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	$63.82	13.671%	$72.5448	$72.54	$72.55	$72.50
Purchase #2	$125.55	12.681%	$141.471	$141.47	$141.45	$141.50
Purchase #3	$72.70	5.582%	$76.7581	$76.76	$76.75	$76.80
Purchase #4	$68.97	10.743%	$76.3794	$76.38	$76.40	$76.40
Purchase #5	$147.85	3.778%	$153.4358	$153.44	$153.45	$153.40
Purchase #6	$35.53	12.187%	$39.86	$39.86	$39.85	$39.90
Purchase #7	$126.62	11.414%	$141.0724	$141.07	$141.05	$141.10
7 purchase totals =	$641.04		$701.5215	$701.52	$701.50	$701.60