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	$35.41	7.560%	$38.087	$38.09	$38.10	$38.10
Purchase #2	$16.80	13.480%	$19.0646	$19.06	$19.05	$19.10
Purchase #3	$115.57	6.570%	$123.1629	$123.16	$123.15	$123.20
Purchase #4	$195.71	6.677%	$208.7776	$208.78	$208.80	$208.80
Purchase #5	$137.38	5.801%	$145.3494	$145.35	$145.35	$145.30
Purchase #6	$41.78	4.150%	$43.5139	$43.51	$43.50	$43.50
Purchase #7	$87.67	9.685%	$96.1608	$96.16	$96.15	$96.20
7 purchase totals =	$630.32		$674.1162	$674.11	$674.10	$674.20