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 $53.46   12.419%   $60.0992   $60.10   $60.10   $60.10  
  Purchase #2 $175.88   12.394%   $197.6786   $197.68   $197.70   $197.70  
  Purchase #3 $114.34   3.368%   $118.191   $118.19   $118.20   $118.20  
  Purchase #4 $214.36   12.399%   $240.9385   $240.94   $240.95   $240.90  
  Purchase #5 $205.60   5.346%   $216.5914   $216.59   $216.60   $216.60  
  Purchase #6 $93.37   11.170%   $103.7994   $103.80   $103.80   $103.80  
  Purchase #7 $100.53   10.431%   $111.0163   $111.02   $111.00   $111.00  
  7 purchase totals = $957.54       $1,048.3144   $1,048.32   $1,048.35   $1,048.30