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 $215.76   9.470%   $236.1925   $236.19   $236.20   $236.20  
  Purchase #2 $187.39   12.766%   $211.3122   $211.31   $211.30   $211.30  
  Purchase #3 $167.34   3.791%   $173.6839   $173.68   $173.70   $173.70  
  Purchase #4 $201.47   6.599%   $214.765   $214.77   $214.75   $214.80  
  Purchase #5 $102.76   4.264%   $107.1417   $107.14   $107.15   $107.10  
  Purchase #6 $150.39   10.521%   $166.2125   $166.21   $166.20   $166.20  
  Purchase #7 $41.30   7.675%   $44.4698   $44.47   $44.45   $44.50  
  7 purchase totals = $1,066.41       $1,153.7776   $1,153.77   $1,153.75   $1,153.80