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 $61.63   3.406%   $63.7291   $63.73   $63.75   $63.70  
  Purchase #2 $196.58   3.127%   $202.7271   $202.73   $202.75   $202.70  
  Purchase #3 $232.85   6.490%   $247.962   $247.96   $247.95   $248.00  
  Purchase #4 $156.54   5.535%   $165.2045   $165.20   $165.20   $165.20  
  Purchase #5 $248.43   6.162%   $263.7383   $263.74   $263.75   $263.70  
  Purchase #6 $182.48   3.263%   $188.4343   $188.43   $188.45   $188.40  
  Purchase #7 $194.75   11.384%   $216.9203   $216.92   $216.90   $216.90  
  7 purchase totals = $1,273.26       $1,348.7156   $1,348.71   $1,348.75   $1,348.60