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 $160.68   3.216%   $165.8475   $165.85   $165.85   $165.80  
  Purchase #2 $51.57   3.617%   $53.4353   $53.44   $53.45   $53.40  
  Purchase #3 $233.92   4.297%   $243.9715   $243.97   $243.95   $244.00  
  Purchase #4 $94.96   13.334%   $107.622   $107.62   $107.60   $107.60  
  Purchase #5 $216.57   11.370%   $241.194   $241.19   $241.20   $241.20  
  Purchase #6 $248.42   4.653%   $259.979   $259.98   $260.00   $260.00  
  Purchase #7 $55.37   8.326%   $59.9801   $59.98   $60.00   $60.00  
  7 purchase totals = $1,061.49       $1,132.0294   $1,132.03   $1,132.05   $1,132.00