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 $83.88   12.612%   $94.4589   $94.46   $94.45   $94.50  
  Purchase #2 $156.62   6.224%   $166.368   $166.37   $166.35   $166.40  
  Purchase #3 $228.58   12.328%   $256.7593   $256.76   $256.75   $256.80  
  Purchase #4 $244.97   8.677%   $266.226   $266.23   $266.25   $266.20  
  Purchase #5 $234.36   4.779%   $245.5601   $245.56   $245.55   $245.60  
  Purchase #6 $193.30   8.506%   $209.7421   $209.74   $209.75   $209.70  
  Purchase #7 $166.90   6.583%   $177.887   $177.89   $177.90   $177.90  
  7 purchase totals = $1,308.61       $1,417.0014   $1,417.01   $1,417.00   $1,417.10