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 $87.58   8.475%   $95.0024   $95.00   $95.00   $95.00  
  Purchase #2 $212.54   12.731%   $239.5985   $239.60   $239.60   $239.60  
  Purchase #3 $104.58   4.361%   $109.1407   $109.14   $109.15   $109.10  
  Purchase #4 $86.95   5.775%   $91.9714   $91.97   $91.95   $92.00  
  Purchase #5 $227.56   8.305%   $246.4589   $246.46   $246.45   $246.50  
  Purchase #6 $65.47   6.357%   $69.6319   $69.63   $69.65   $69.60  
  Purchase #7 $90.37   4.126%   $94.0987   $94.10   $94.10   $94.10  
  7 purchase totals = $875.05       $945.9025   $945.90   $945.90   $945.90