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 $91.71   3.256%   $94.6961   $94.70   $94.70   $94.70  
  Purchase #2 $8.71   11.181%   $9.6839   $9.68   $9.70   $9.70  
  Purchase #3 $79.67   3.561%   $82.507   $82.51   $82.50   $82.50  
  Purchase #4 $141.60   10.427%   $156.3646   $156.36   $156.35   $156.40  
  Purchase #5 $145.53   12.563%   $163.8129   $163.81   $163.80   $163.80  
  Purchase #6 $183.51   13.333%   $207.9774   $207.98   $208.00   $208.00  
  Purchase #7 $39.55   3.355%   $40.8769   $40.88   $40.90   $40.90  
  7 purchase totals = $690.28       $755.9188   $755.92   $755.95   $756.00