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 $183.32   4.764%   $192.0534   $192.05   $192.05   $192.10  
  Purchase #2 $202.78   6.696%   $216.3581   $216.36   $216.35   $216.40  
  Purchase #3 $31.45   11.282%   $34.9982   $35.00   $35.00   $35.00  
  Purchase #4 $115.90   8.434%   $125.675   $125.68   $125.70   $125.70  
  Purchase #5 $241.60   8.510%   $262.1602   $262.16   $262.15   $262.20  
  Purchase #6 $201.75   13.109%   $228.1974   $228.20   $228.20   $228.20  
  Purchase #7 $31.49   8.106%   $34.0426   $34.04   $34.05   $34.00  
  7 purchase totals = $1,008.29       $1,093.4849   $1,093.49   $1,093.50   $1,093.60