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 $114.66   4.545%   $119.8713   $119.87   $119.85   $119.90  
  Purchase #2 $190.27   11.194%   $211.5688   $211.57   $211.55   $211.60  
  Purchase #3 $135.56   12.173%   $152.0617   $152.06   $152.05   $152.10  
  Purchase #4 $209.92   4.582%   $219.5385   $219.54   $219.55   $219.50  
  Purchase #5 $17.51   9.361%   $19.1491   $19.15   $19.15   $19.10  
  Purchase #6 $83.86   13.538%   $95.213   $95.21   $95.20   $95.20  
  Purchase #7 $62.95   4.297%   $65.655   $65.66   $65.65   $65.70  
  7 purchase totals = $814.73       $883.0574   $883.06   $883.00   $883.10