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 $63.35   5.801%   $67.0249   $67.02   $67.00   $67.00  
  Purchase #2 $238.71   6.517%   $254.2667   $254.27   $254.25   $254.30  
  Purchase #3 $165.40   8.549%   $179.54   $179.54   $179.55   $179.50  
  Purchase #4 $160.47   13.307%   $181.8237   $181.82   $181.80   $181.80  
  Purchase #5 $126.54   9.687%   $138.7979   $138.80   $138.80   $138.80  
  Purchase #6 $201.35   4.561%   $210.5336   $210.53   $210.55   $210.50  
  Purchase #7 $67.67   9.241%   $73.9234   $73.92   $73.90   $73.90  
  7 purchase totals = $1,023.49       $1,105.9102   $1,105.90   $1,105.85   $1,105.80