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 $90.62   5.860%   $95.9303   $95.93   $95.95   $95.90  
  Purchase #2 $215.37   4.637%   $225.3567   $225.36   $225.35   $225.40  
  Purchase #3 $58.69   7.212%   $62.9227   $62.92   $62.90   $62.90  
  Purchase #4 $6.32   7.730%   $6.8085   $6.81   $6.80   $6.80  
  Purchase #5 $40.93   7.589%   $44.0362   $44.04   $44.05   $44.00  
  Purchase #6 $42.71   7.479%   $45.9043   $45.90   $45.90   $45.90  
  Purchase #7 $246.81   10.318%   $272.2759   $272.28   $272.30   $272.30  
  7 purchase totals = $701.45       $753.2346   $753.24   $753.25   $753.20