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 $114.65   4.342%   $119.6281   $119.63   $119.65   $119.60  
  Purchase #2 $104.32   4.302%   $108.8078   $108.81   $108.80   $108.80  
  Purchase #3 $212.88   4.200%   $221.821   $221.82   $221.80   $221.80  
  Purchase #4 $205.91   5.702%   $217.651   $217.65   $217.65   $217.70  
  Purchase #5 $86.62   6.170%   $91.9645   $91.96   $91.95   $92.00  
  Purchase #6 $93.48   6.303%   $99.372   $99.37   $99.35   $99.40  
  Purchase #7 $144.62   11.609%   $161.4089   $161.41   $161.40   $161.40  
  7 purchase totals = $962.48       $1,020.6533   $1,020.65   $1,020.60   $1,020.70