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 $61.41   13.500%   $69.7004   $69.70   $69.70   $69.70  
  Purchase #2 $118.56   6.584%   $126.366   $126.37   $126.35   $126.40  
  Purchase #3 $159.84   10.209%   $176.1581   $176.16   $176.15   $176.20  
  Purchase #4 $103.31   10.256%   $113.9055   $113.91   $113.90   $113.90  
  Purchase #5 $205.90   3.769%   $213.6604   $213.66   $213.65   $213.70  
  Purchase #6 $85.95   3.321%   $88.8044   $88.80   $88.80   $88.80  
  Purchase #7 $70.52   7.151%   $75.5629   $75.56   $75.55   $75.60  
  7 purchase totals = $805.49       $864.1577   $864.16   $864.10   $864.30