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 $219.44   11.672%   $245.053   $245.05   $245.05   $245.10  
  Purchase #2 $185.59   8.664%   $201.6695   $201.67   $201.65   $201.70  
  Purchase #3 $157.47   7.644%   $169.507   $169.51   $169.50   $169.50  
  Purchase #4 $19.62   4.793%   $20.5604   $20.56   $20.55   $20.60  
  Purchase #5 $189.31   6.500%   $201.6152   $201.62   $201.60   $201.60  
  Purchase #6 $182.84   9.318%   $199.877   $199.88   $199.90   $199.90  
  Purchase #7 $178.93   3.524%   $185.2355   $185.24   $185.25   $185.20  
  7 purchase totals = $1,133.20       $1,223.5176   $1,223.53   $1,223.50   $1,223.60