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 $204.95   4.713%   $214.6093   $214.61   $214.60   $214.60  
  Purchase #2 $229.86   4.281%   $239.7003   $239.70   $239.70   $239.70  
  Purchase #3 $204.96   6.357%   $217.9893   $217.99   $218.00   $218.00  
  Purchase #4 $91.88   4.463%   $95.9806   $95.98   $96.00   $96.00  
  Purchase #5 $131.48   11.752%   $146.9315   $146.93   $146.95   $146.90  
  Purchase #6 $133.57   12.117%   $149.7547   $149.75   $149.75   $149.80  
  Purchase #7 $44.50   6.149%   $47.2363   $47.24   $47.25   $47.20  
  7 purchase totals = $1,041.20       $1,112.2020   $1,112.20   $1,112.25   $1,112.20