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 $60.38   7.595%   $64.9659   $64.97   $64.95   $65.00  
  Purchase #2 $125.49   7.551%   $134.9657   $134.97   $134.95   $135.00  
  Purchase #3 $141.87   10.551%   $156.8387   $156.84   $156.85   $156.80  
  Purchase #4 $8.95   7.414%   $9.6136   $9.61   $9.60   $9.60  
  Purchase #5 $215.82   4.405%   $225.3269   $225.33   $225.35   $225.30  
  Purchase #6 $246.88   3.546%   $255.6344   $255.63   $255.65   $255.60  
  Purchase #7 $24.61   5.348%   $25.9261   $25.93   $25.95   $25.90  
  7 purchase totals = $824.00       $873.2713   $873.28   $873.30   $873.20