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 $58.45   6.473%   $62.2335   $62.23   $62.25   $62.20  
  Purchase #2 $140.35   7.532%   $150.9212   $150.92   $150.90   $150.90  
  Purchase #3 $51.34   11.392%   $57.1887   $57.19   $57.20   $57.20  
  Purchase #4 $201.73   4.298%   $210.4004   $210.40   $210.40   $210.40  
  Purchase #5 $164.49   4.869%   $172.499   $172.50   $172.50   $172.50  
  Purchase #6 $123.88   10.307%   $136.6483   $136.65   $136.65   $136.60  
  Purchase #7 $203.53   5.654%   $215.0376   $215.04   $215.05   $215.00  
  7 purchase totals = $943.77       $1,004.9287   $1,004.93   $1,004.95   $1,004.80