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 $212.30   6.780%   $226.6939   $226.69   $226.70   $226.70  
  Purchase #2 $121.31   5.350%   $127.8001   $127.80   $127.80   $127.80  
  Purchase #3 $58.25   11.516%   $64.9581   $64.96   $64.95   $65.00  
  Purchase #4 $200.69   7.505%   $215.7518   $215.75   $215.75   $215.80  
  Purchase #5 $187.83   8.796%   $204.3515   $204.35   $204.35   $204.40  
  Purchase #6 $40.42   4.686%   $42.3141   $42.31   $42.30   $42.30  
  Purchase #7 $134.36   12.241%   $150.807   $150.81   $150.80   $150.80  
  7 purchase totals = $955.16       $1,032.6765   $1,032.67   $1,032.65   $1,032.80