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 $65.36   9.725%   $71.7163   $71.72   $71.70   $71.70  
  Purchase #2 $74.66   3.397%   $77.1962   $77.20   $77.20   $77.20  
  Purchase #3 $148.70   7.275%   $159.5179   $159.52   $159.50   $159.50  
  Purchase #4 $58.82   3.465%   $60.8581   $60.86   $60.85   $60.90  
  Purchase #5 $249.51   6.373%   $265.4113   $265.41   $265.40   $265.40  
  Purchase #6 $190.88   5.467%   $201.3154   $201.32   $201.30   $201.30  
  Purchase #7 $107.79   4.727%   $112.8852   $112.89   $112.90   $112.90  
  7 purchase totals = $895.72       $948.9004   $948.92   $948.85   $948.90