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 $23.59   4.393%   $24.6263   $24.63   $24.65   $24.60  
  Purchase #2 $222.35   4.637%   $232.6604   $232.66   $232.65   $232.70  
  Purchase #3 $62.94   12.784%   $70.9862   $70.99   $71.00   $71.00  
  Purchase #4 $206.50   13.586%   $234.5551   $234.56   $234.55   $234.60  
  Purchase #5 $97.76   3.227%   $100.9147   $100.91   $100.90   $100.90  
  Purchase #6 $178.41   12.416%   $200.5614   $200.56   $200.55   $200.60  
  Purchase #7 $161.60   5.365%   $170.2698   $170.27   $170.25   $170.30  
  7 purchase totals = $953.15       $1,034.5739   $1,034.58   $1,034.55   $1,034.70