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 $91.36   4.349%   $95.3332   $95.33   $95.35   $95.30  
  Purchase #2 $200.86   6.369%   $213.6528   $213.65   $213.65   $213.70  
  Purchase #3 $208.38   12.535%   $234.5004   $234.50   $234.50   $234.50  
  Purchase #4 $203.59   9.630%   $223.1957   $223.20   $223.20   $223.20  
  Purchase #5 $52.56   8.475%   $57.0145   $57.01   $57.00   $57.00  
  Purchase #6 $236.83   8.414%   $256.7569   $256.76   $256.75   $256.80  
  Purchase #7 $26.48   10.416%   $29.2382   $29.24   $29.25   $29.20  
  7 purchase totals = $1,020.06       $1,109.6917   $1,109.69   $1,109.70   $1,109.70