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 $165.62   7.198%   $177.5413   $177.54   $177.55   $177.50  
  Purchase #2 $242.73   7.252%   $260.3328   $260.33   $260.35   $260.30  
  Purchase #3 $158.31   13.284%   $179.3399   $179.34   $179.35   $179.30  
  Purchase #4 $127.47   4.764%   $133.5427   $133.54   $133.55   $133.50  
  Purchase #5 $41.37   4.558%   $43.2556   $43.26   $43.25   $43.30  
  Purchase #6 $191.97   6.737%   $204.903   $204.90   $204.90   $204.90  
  Purchase #7 $106.56   8.808%   $115.9458   $115.95   $115.95   $115.90  
  7 purchase totals = $1,034.03       $1,114.8611   $1,114.86   $1,114.90   $1,114.70