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 $222.76   10.643%   $246.4683   $246.47   $246.45   $246.50  
  Purchase #2 $191.77   6.682%   $204.5841   $204.58   $204.60   $204.60  
  Purchase #3 $9.92   8.466%   $10.7598   $10.76   $10.75   $10.80  
  Purchase #4 $67.58   8.280%   $73.1756   $73.18   $73.20   $73.20  
  Purchase #5 $57.97   13.656%   $65.8864   $65.89   $65.90   $65.90  
  Purchase #6 $216.26   6.630%   $230.598   $230.60   $230.60   $230.60  
  Purchase #7 $209.82   9.324%   $229.3836   $229.38   $229.40   $229.40  
  7 purchase totals = $976.08       $1,060.8558   $1,060.86   $1,060.90   $1,061.00