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 $62.81   6.155%   $66.676   $66.68   $66.70   $66.70  
  Purchase #2 $145.32   6.223%   $154.3633   $154.36   $154.35   $154.40  
  Purchase #3 $64.81   11.749%   $72.4245   $72.42   $72.40   $72.40  
  Purchase #4 $199.64   6.200%   $212.0177   $212.02   $212.00   $212.00  
  Purchase #5 $161.25   4.721%   $168.8626   $168.86   $168.85   $168.90  
  Purchase #6 $45.51   7.213%   $48.7926   $48.79   $48.80   $48.80  
  Purchase #7 $26.50   9.225%   $28.9446   $28.94   $28.95   $28.90  
  7 purchase totals = $705.84       $752.0813   $752.07   $752.05   $752.10