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 $153.39   10.630%   $169.6954   $169.70   $169.70   $169.70  
  Purchase #2 $240.90   12.634%   $271.3353   $271.34   $271.35   $271.30  
  Purchase #3 $133.60   7.769%   $143.9794   $143.98   $144.00   $144.00  
  Purchase #4 $25.39   5.584%   $26.8078   $26.81   $26.80   $26.80  
  Purchase #5 $37.93   7.620%   $40.8203   $40.82   $40.80   $40.80  
  Purchase #6 $218.29   7.817%   $235.3537   $235.35   $235.35   $235.40  
  Purchase #7 $218.36   8.660%   $237.27   $237.27   $237.25   $237.30  
  7 purchase totals = $1,027.86       $1,125.2619   $1,125.27   $1,125.25   $1,125.30