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	$115.62	11.314%	$128.7012	$128.70	$128.70	$128.70
Purchase #2	$143.90	10.148%	$158.503	$158.50	$158.50	$158.50
Purchase #3	$132.29	12.472%	$148.7892	$148.79	$148.80	$148.80
Purchase #4	$244.63	8.384%	$265.1398	$265.14	$265.15	$265.10
Purchase #5	$33.96	5.528%	$35.8373	$35.84	$35.85	$35.80
Purchase #6	$144.58	13.806%	$164.5407	$164.54	$164.55	$164.50
Purchase #7	$234.61	13.801%	$266.9885	$266.99	$267.00	$267.00
7 purchase totals =	$1,049.59		$1,168.4997	$1,168.50	$1,168.55	$1,168.40