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	$32.44	9.176%	$35.4167	$35.42	$35.40	$35.40
Purchase #2	$133.55	13.868%	$152.0707	$152.07	$152.05	$152.10
Purchase #3	$178.70	3.489%	$184.9348	$184.93	$184.95	$184.90
Purchase #4	$93.29	10.757%	$103.3252	$103.33	$103.35	$103.30
Purchase #5	$43.72	9.335%	$47.8013	$47.80	$47.80	$47.80
Purchase #6	$74.98	10.492%	$82.8469	$82.85	$82.85	$82.80
Purchase #7	$150.56	3.299%	$155.527	$155.53	$155.55	$155.50
7 purchase totals =	$707.24		$761.9226	$761.93	$761.95	$761.80