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 $85.83   9.515%   $93.9967   $94.00   $94.00   $94.00  
  Purchase #2 $136.31   13.816%   $155.1426   $155.14   $155.15   $155.10  
  Purchase #3 $44.63   7.403%   $47.934   $47.93   $47.95   $47.90  
  Purchase #4 $105.90   3.281%   $109.3746   $109.37   $109.35   $109.40  
  Purchase #5 $31.59   10.468%   $34.8968   $34.90   $34.90   $34.90  
  Purchase #6 $181.70   13.713%   $206.6165   $206.62   $206.60   $206.60  
  Purchase #7 $72.42   4.351%   $75.571   $75.57   $75.55   $75.60  
  7 purchase totals = $658.38       $723.5322   $723.53   $723.50   $723.50