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	$180.57	3.561%	$187.0001	$187.00	$187.00	$187.00
Purchase #2	$198.30	8.383%	$214.9235	$214.92	$214.90	$214.90
Purchase #3	$77.81	7.871%	$83.9344	$83.93	$83.95	$83.90
Purchase #4	$226.95	12.401%	$255.0941	$255.09	$255.10	$255.10
Purchase #5	$160.26	11.308%	$178.3822	$178.38	$178.40	$178.40
Purchase #6	$95.48	5.105%	$100.3543	$100.35	$100.35	$100.40
Purchase #7	$31.36	13.403%	$35.5632	$35.56	$35.55	$35.60
7 purchase totals =	$970.73		$1,055.2518	$1,055.23	$1,055.25	$1,055.30