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 $219.52   6.853%   $234.5637   $234.56   $234.55   $234.60  
  Purchase #2 $248.53   6.442%   $264.5403   $264.54   $264.55   $264.50  
  Purchase #3 $206.84   4.403%   $215.9472   $215.95   $215.95   $215.90  
  Purchase #4 $8.25   7.763%   $8.8904   $8.89   $8.90   $8.90  
  Purchase #5 $8.26   6.329%   $8.7828   $8.78   $8.80   $8.80  
  Purchase #6 $177.57   12.867%   $200.4179   $200.42   $200.40   $200.40  
  Purchase #7 $150.51   13.732%   $171.178   $171.18   $171.20   $171.20  
  7 purchase totals = $1,019.48       $1,104.3203   $1,104.32   $1,104.35   $1,104.30