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	$119.76	3.377%	$123.8043	$123.80	$123.80	$123.80
Purchase #2	$33.66	5.427%	$35.4867	$35.49	$35.50	$35.50
Purchase #3	$242.85	8.686%	$263.944	$263.94	$263.95	$263.90
Purchase #4	$50.81	11.732%	$56.771	$56.77	$56.75	$56.80
Purchase #5	$129.89	9.667%	$142.4465	$142.45	$142.45	$142.40
Purchase #6	$137.28	12.546%	$154.5031	$154.50	$154.50	$154.50
Purchase #7	$158.37	7.237%	$169.8312	$169.83	$169.85	$169.80
7 purchase totals =	$872.62		$946.7868	$946.78	$946.80	$946.70