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 $89.73   4.812%   $94.0478   $94.05   $94.05   $94.00  
  Purchase #2 $62.32   11.197%   $69.298   $69.30   $69.30   $69.30  
  Purchase #3 $59.31   6.618%   $63.2351   $63.24   $63.25   $63.20  
  Purchase #4 $240.36   6.299%   $255.5003   $255.50   $255.50   $255.50  
  Purchase #5 $210.75   7.563%   $226.689   $226.69   $226.70   $226.70  
  Purchase #6 $131.69   10.490%   $145.5043   $145.50   $145.50   $145.50  
  Purchase #7 $161.33   12.305%   $181.1817   $181.18   $181.20   $181.20  
  7 purchase totals = $955.49       $1,035.4562   $1,035.46   $1,035.50   $1,035.40