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	$112.50	9.661%	$123.3686	$123.37	$123.35	$123.40
Purchase #2	$217.71	11.384%	$242.4941	$242.49	$242.50	$242.50
Purchase #3	$223.78	13.104%	$253.1041	$253.10	$253.10	$253.10
Purchase #4	$193.86	3.526%	$200.6955	$200.70	$200.70	$200.70
Purchase #5	$105.73	13.778%	$120.2975	$120.30	$120.30	$120.30
Purchase #6	$111.29	7.450%	$119.5811	$119.58	$119.60	$119.60
Purchase #7	$25.55	12.661%	$28.7849	$28.78	$28.80	$28.80
7 purchase totals =	$990.42		$1,088.3258	$1,088.32	$1,088.35	$1,088.40