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	$67.60	6.441%	$71.9541	$71.95	$71.95	$72.00
Purchase #2	$35.59	7.369%	$38.2126	$38.21	$38.20	$38.20
Purchase #3	$49.99	4.322%	$52.1506	$52.15	$52.15	$52.20
Purchase #4	$66.93	6.426%	$71.2309	$71.23	$71.25	$71.20
Purchase #5	$6.60	11.796%	$7.3785	$7.38	$7.40	$7.40
Purchase #6	$123.70	10.146%	$136.2506	$136.25	$136.25	$136.30
Purchase #7	$43.90	10.104%	$48.3357	$48.34	$48.35	$48.30
7 purchase totals =	$394.31		$425.5130	$425.51	$425.55	$425.60