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 $173.97   13.620%   $197.6647   $197.66   $197.65   $197.70  
  Purchase #2 $59.66   4.321%   $62.2379   $62.24   $62.25   $62.20  
  Purchase #3 $230.75   7.272%   $247.5301   $247.53   $247.55   $247.50  
  Purchase #4 $60.92   8.409%   $66.0428   $66.04   $66.05   $66.00  
  Purchase #5 $110.36   8.348%   $119.5729   $119.57   $119.55   $119.60  
  Purchase #6 $235.62   12.206%   $264.3798   $264.38   $264.40   $264.40  
  Purchase #7 $143.31   8.775%   $155.8855   $155.89   $155.90   $155.90  
  7 purchase totals = $1,014.59       $1,113.3137   $1,113.31   $1,113.35   $1,113.30