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	$28.82	12.160%	$32.3245	$32.32	$32.30	$32.30
Purchase #2	$119.74	9.762%	$131.429	$131.43	$131.45	$131.40
Purchase #3	$180.32	8.701%	$196.0096	$196.01	$196.00	$196.00
Purchase #4	$35.66	8.305%	$38.6216	$38.62	$38.60	$38.60
Purchase #5	$188.77	7.631%	$203.175	$203.18	$203.20	$203.20
Purchase #6	$39.70	11.774%	$44.3743	$44.37	$44.35	$44.40
Purchase #7	$31.58	13.568%	$35.8648	$35.86	$35.85	$35.90
7 purchase totals =	$624.59		$681.7988	$681.79	$681.75	$681.80