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	$204.79	10.428%	$226.1455	$226.15	$226.15	$226.10
Purchase #2	$200.58	6.114%	$212.8435	$212.84	$212.85	$212.80
Purchase #3	$246.25	11.607%	$274.8322	$274.83	$274.85	$274.80
Purchase #4	$83.60	8.262%	$90.507	$90.51	$90.50	$90.50
Purchase #5	$97.84	3.137%	$100.9092	$100.91	$100.90	$100.90
Purchase #6	$153.57	11.760%	$171.6298	$171.63	$171.65	$171.60
Purchase #7	$73.29	7.519%	$78.8007	$78.80	$78.80	$78.80
7 purchase totals =	$1,059.92		$1,155.6679	$1,155.67	$1,155.70	$1,155.50