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 $61.26   5.825%   $64.8284   $64.83   $64.85   $64.80  
  Purchase #2 $119.93   9.781%   $131.6604   $131.66   $131.65   $131.70  
  Purchase #3 $133.89   9.155%   $146.1476   $146.15   $146.15   $146.10  
  Purchase #4 $231.53   6.544%   $246.6813   $246.68   $246.70   $246.70  
  Purchase #5 $128.35   13.392%   $145.5386   $145.54   $145.55   $145.50  
  Purchase #6 $184.28   10.840%   $204.256   $204.26   $204.25   $204.30  
  Purchase #7 $216.82   7.227%   $232.4896   $232.49   $232.50   $232.50  
  7 purchase totals = $1,076.06       $1,171.6019   $1,171.61   $1,171.65   $1,171.60