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 $226.85   4.563%   $237.2012   $237.20   $237.20   $237.20  
  Purchase #2 $70.70   7.385%   $75.9212   $75.92   $75.90   $75.90  
  Purchase #3 $145.69   3.422%   $150.6755   $150.68   $150.70   $150.70  
  Purchase #4 $75.40   10.320%   $83.1813   $83.18   $83.20   $83.20  
  Purchase #5 $95.80   11.118%   $106.451   $106.45   $106.45   $106.50  
  Purchase #6 $107.85   8.374%   $116.8814   $116.88   $116.90   $116.90  
  Purchase #7 $113.61   9.831%   $124.779   $124.78   $124.80   $124.80  
  7 purchase totals = $835.90       $895.0906   $895.09   $895.15   $895.20