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 $174.27   12.235%   $195.5919   $195.59   $195.60   $195.60  
  Purchase #2 $118.68   8.146%   $128.3477   $128.35   $128.35   $128.30  
  Purchase #3 $66.49   4.778%   $69.6669   $69.67   $69.65   $69.70  
  Purchase #4 $124.31   11.348%   $138.4167   $138.42   $138.40   $138.40  
  Purchase #5 $23.34   4.713%   $24.44   $24.44   $24.45   $24.40  
  Purchase #6 $238.54   12.741%   $268.9324   $268.93   $268.95   $268.90  
  Purchase #7 $107.26   11.507%   $119.6024   $119.60   $119.60   $119.60  
  7 purchase totals = $852.89       $944.9980   $945.00   $945.00   $944.90