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 $91.95   3.497%   $95.1655   $95.17   $95.15   $95.20  
  Purchase #2 $91.42   8.126%   $98.8488   $98.85   $98.85   $98.80  
  Purchase #3 $246.28   5.671%   $260.2465   $260.25   $260.25   $260.20  
  Purchase #4 $54.48   3.272%   $56.2626   $56.26   $56.25   $56.30  
  Purchase #5 $117.54   3.661%   $121.8431   $121.84   $121.85   $121.80  
  Purchase #6 $54.35   4.576%   $56.8371   $56.84   $56.85   $56.80  
  Purchase #7 $14.38   13.216%   $16.2805   $16.28   $16.30   $16.30  
  7 purchase totals = $670.40       $705.4841   $705.49   $705.50   $705.40