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	$17.48	9.569%	$19.1527	$19.15	$19.15	$19.20
Purchase #2	$41.97	8.302%	$45.4543	$45.45	$45.45	$45.50
Purchase #3	$236.45	5.134%	$248.5893	$248.59	$248.60	$248.60
Purchase #4	$129.88	10.811%	$143.9213	$143.92	$143.90	$143.90
Purchase #5	$90.49	12.614%	$101.9044	$101.90	$101.90	$101.90
Purchase #6	$199.29	11.592%	$222.3917	$222.39	$222.40	$222.40
Purchase #7	$106.36	7.670%	$114.5178	$114.52	$114.50	$114.50
7 purchase totals =	$821.92		$895.9315	$895.92	$895.90	$896.00