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 $215.74   5.301%   $227.1764   $227.18   $227.20   $227.20  
  Purchase #2 $141.87   10.562%   $156.8543   $156.85   $156.85   $156.90  
  Purchase #3 $160.61   5.626%   $169.6459   $169.65   $169.65   $169.60  
  Purchase #4 $25.70   10.855%   $28.4897   $28.49   $28.50   $28.50  
  Purchase #5 $232.62   12.718%   $262.2046   $262.20   $262.20   $262.20  
  Purchase #6 $151.90   3.283%   $156.8869   $156.89   $156.90   $156.90  
  Purchase #7 $173.62   11.859%   $194.2096   $194.21   $194.20   $194.20  
  7 purchase totals = $1,102.06       $1,195.4674   $1,195.47   $1,195.50   $1,195.50