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	$99.44	10.471%	$109.8524	$109.85	$109.85	$109.90
Purchase #2	$72.56	8.585%	$78.7893	$78.79	$78.80	$78.80
Purchase #3	$38.31	4.450%	$40.0148	$40.01	$40.00	$40.00
Purchase #4	$231.61	13.576%	$263.0534	$263.05	$263.05	$263.10
Purchase #5	$209.93	4.470%	$219.3139	$219.31	$219.30	$219.30
Purchase #6	$155.29	5.520%	$163.862	$163.86	$163.85	$163.90
Purchase #7	$95.48	6.867%	$102.0366	$102.04	$102.05	$102.00
7 purchase totals =	$902.62		$976.9224	$976.91	$976.90	$977.00