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 $243.97   7.521%   $262.319   $262.32   $262.30   $262.30  
  Purchase #2 $182.62   6.418%   $194.3406   $194.34   $194.35   $194.30  
  Purchase #3 $58.56   7.494%   $62.9485   $62.95   $62.95   $62.90  
  Purchase #4 $163.94   11.831%   $183.3357   $183.34   $183.35   $183.30  
  Purchase #5 $187.63   8.662%   $203.8825   $203.88   $203.90   $203.90  
  Purchase #6 $52.49   12.467%   $59.0339   $59.03   $59.05   $59.00  
  Purchase #7 $165.33   4.721%   $173.1352   $173.14   $173.15   $173.10  
  7 purchase totals = $1,054.54       $1,138.9954   $1,139.00   $1,139.05   $1,138.80