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 $31.94   5.257%   $33.6191   $33.62   $33.60   $33.60  
  Purchase #2 $195.98   3.569%   $202.9745   $202.97   $202.95   $203.00  
  Purchase #3 $185.35   4.553%   $193.789   $193.79   $193.80   $193.80  
  Purchase #4 $159.67   4.581%   $166.9845   $166.98   $167.00   $167.00  
  Purchase #5 $70.88   5.368%   $74.6848   $74.68   $74.70   $74.70  
  Purchase #6 $234.39   9.578%   $256.8399   $256.84   $256.85   $256.80  
  Purchase #7 $186.51   9.811%   $204.8085   $204.81   $204.80   $204.80  
  7 purchase totals = $1,064.72       $1,133.7003   $1,133.69   $1,133.70   $1,133.70