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 $87.32   7.642%   $93.993   $93.99   $94.00   $94.00  
  Purchase #2 $204.48   9.167%   $223.2247   $223.22   $223.20   $223.20  
  Purchase #3 $173.43   3.221%   $179.0162   $179.02   $179.00   $179.00  
  Purchase #4 $206.62   9.139%   $225.503   $225.50   $225.50   $225.50  
  Purchase #5 $190.73   12.201%   $214.001   $214.00   $214.00   $214.00  
  Purchase #6 $151.97   8.545%   $164.9558   $164.96   $164.95   $165.00  
  Purchase #7 $183.49   11.849%   $205.2317   $205.23   $205.25   $205.20  
  7 purchase totals = $1,198.04       $1,305.9254   $1,305.92   $1,305.90   $1,305.90