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 $60.59   4.126%   $63.0899   $63.09   $63.10   $63.10  
  Purchase #2 $233.63   7.148%   $250.3299   $250.33   $250.35   $250.30  
  Purchase #3 $120.74   3.789%   $125.3148   $125.31   $125.30   $125.30  
  Purchase #4 $10.95   8.860%   $11.9202   $11.92   $11.90   $11.90  
  Purchase #5 $54.86   11.211%   $61.0104   $61.01   $61.00   $61.00  
  Purchase #6 $42.98   7.398%   $46.1597   $46.16   $46.15   $46.20  
  Purchase #7 $177.89   11.416%   $198.1979   $198.20   $198.20   $198.20  
  7 purchase totals = $701.64       $756.0228   $756.02   $756.00   $756.00