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 $86.63   10.202%   $95.468   $95.47   $95.45   $95.50  
  Purchase #2 $59.56   9.794%   $65.3933   $65.39   $65.40   $65.40  
  Purchase #3 $151.76   3.263%   $156.7119   $156.71   $156.70   $156.70  
  Purchase #4 $168.97   6.147%   $179.3566   $179.36   $179.35   $179.40  
  Purchase #5 $31.62   9.241%   $34.542   $34.54   $34.55   $34.50  
  Purchase #6 $149.68   4.864%   $156.9604   $156.96   $156.95   $157.00  
  Purchase #7 $16.86   10.266%   $18.5908   $18.59   $18.60   $18.60  
  7 purchase totals = $665.08       $707.0230   $707.02   $707.00   $707.10