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 $13.46   5.477%   $14.1972   $14.20   $14.20   $14.20  
  Purchase #2 $202.34   10.546%   $223.6788   $223.68   $223.70   $223.70  
  Purchase #3 $196.63   7.293%   $210.9702   $210.97   $210.95   $211.00  
  Purchase #4 $94.64   4.416%   $98.8193   $98.82   $98.80   $98.80  
  Purchase #5 $190.37   4.401%   $198.7482   $198.75   $198.75   $198.70  
  Purchase #6 $130.50   6.199%   $138.5897   $138.59   $138.60   $138.60  
  Purchase #7 $128.26   9.729%   $140.7384   $140.74   $140.75   $140.70  
  7 purchase totals = $956.20       $1,025.7418   $1,025.75   $1,025.75   $1,025.70