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 $56.70   9.344%   $61.998   $62.00   $62.00   $62.00  
  Purchase #2 $212.66   5.306%   $223.9437   $223.94   $223.95   $223.90  
  Purchase #3 $145.56   9.799%   $159.8234   $159.82   $159.80   $159.80  
  Purchase #4 $209.39   3.372%   $216.4506   $216.45   $216.45   $216.50  
  Purchase #5 $59.93   5.243%   $63.0721   $63.07   $63.05   $63.10  
  Purchase #6 $99.53   13.210%   $112.6779   $112.68   $112.70   $112.70  
  Purchase #7 $8.87   9.575%   $9.7193   $9.72   $9.70   $9.70  
  7 purchase totals = $792.64       $847.6850   $847.68   $847.65   $847.70