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	$94.98	3.671%	$98.4667	$98.47	$98.45	$98.50
Purchase #2	$206.89	6.837%	$221.0351	$221.04	$221.05	$221.00
Purchase #3	$122.57	13.484%	$139.0973	$139.10	$139.10	$139.10
Purchase #4	$99.74	6.620%	$106.3428	$106.34	$106.35	$106.30
Purchase #5	$69.29	4.778%	$72.6007	$72.60	$72.60	$72.60
Purchase #6	$143.89	7.642%	$154.8861	$154.89	$154.90	$154.90
Purchase #7	$241.95	8.703%	$263.0069	$263.01	$263.00	$263.00
7 purchase totals =	$979.31		$1,055.4356	$1,055.45	$1,055.45	$1,055.40