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 $87.59   8.448%   $94.9896   $94.99   $95.00   $95.00  
  Purchase #2 $245.48   10.731%   $271.8225   $271.82   $271.80   $271.80  
  Purchase #3 $81.51   5.174%   $85.7273   $85.73   $85.75   $85.70  
  Purchase #4 $211.31   6.678%   $225.4213   $225.42   $225.40   $225.40  
  Purchase #5 $50.29   9.798%   $55.2174   $55.22   $55.20   $55.20  
  Purchase #6 $46.72   9.132%   $50.9865   $50.99   $51.00   $51.00  
  Purchase #7 $46.50   5.702%   $49.1514   $49.15   $49.15   $49.20  
  7 purchase totals = $769.40       $833.3160   $833.32   $833.30   $833.30