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 $42.95   9.431%   $47.0006   $47.00   $47.00   $47.00  
  Purchase #2 $147.29   10.397%   $162.6037   $162.60   $162.60   $162.60  
  Purchase #3 $164.77   9.355%   $180.1842   $180.18   $180.20   $180.20  
  Purchase #4 $234.88   5.507%   $247.8148   $247.81   $247.80   $247.80  
  Purchase #5 $32.99   5.337%   $34.7507   $34.75   $34.75   $34.80  
  Purchase #6 $207.49   8.144%   $224.388   $224.39   $224.40   $224.40  
  Purchase #7 $154.65   7.759%   $166.6493   $166.65   $166.65   $166.60  
  7 purchase totals = $985.02       $1,063.3913   $1,063.38   $1,063.40   $1,063.40