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 $57.34   9.310%   $62.6784   $62.68   $62.70   $62.70  
  Purchase #2 $181.89   11.759%   $203.2784   $203.28   $203.30   $203.30  
  Purchase #3 $76.38   5.566%   $80.6313   $80.63   $80.65   $80.60  
  Purchase #4 $145.29   4.308%   $151.5491   $151.55   $151.55   $151.50  
  Purchase #5 $225.47   4.193%   $234.924   $234.92   $234.90   $234.90  
  Purchase #6 $216.56   5.752%   $229.0165   $229.02   $229.00   $229.00  
  Purchase #7 $129.86   4.373%   $135.5388   $135.54   $135.55   $135.50  
  7 purchase totals = $1,032.79       $1,097.6165   $1,097.62   $1,097.65   $1,097.50