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	$162.77	5.687%	$172.0267	$172.03	$172.05	$172.00
Purchase #2	$44.88	8.510%	$48.6993	$48.70	$48.70	$48.70
Purchase #3	$108.38	11.240%	$120.5619	$120.56	$120.55	$120.60
Purchase #4	$200.71	3.816%	$208.3691	$208.37	$208.35	$208.40
Purchase #5	$31.91	12.359%	$35.8538	$35.85	$35.85	$35.90
Purchase #6	$225.65	6.672%	$240.7054	$240.71	$240.70	$240.70
Purchase #7	$43.66	3.448%	$45.1654	$45.17	$45.15	$45.20
7 purchase totals =	$817.96		$871.3816	$871.39	$871.35	$871.50