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	$136.77	5.194%	$143.8738	$143.87	$143.85	$143.90
Purchase #2	$150.56	7.314%	$161.572	$161.57	$161.55	$161.60
Purchase #3	$238.67	10.625%	$264.0287	$264.03	$264.05	$264.00
Purchase #4	$33.37	7.451%	$35.8564	$35.86	$35.85	$35.90
Purchase #5	$20.57	3.264%	$21.2414	$21.24	$21.25	$21.20
Purchase #6	$225.59	7.534%	$242.586	$242.59	$242.60	$242.60
Purchase #7	$131.88	6.743%	$140.7727	$140.77	$140.75	$140.80
7 purchase totals =	$937.41		$1,009.9310	$1,009.93	$1,009.90	$1,010.00