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 $88.92   6.862%   $95.0217   $95.02   $95.00   $95.00  
  Purchase #2 $216.47   8.669%   $235.2358   $235.24   $235.25   $235.20  
  Purchase #3 $51.37   6.576%   $54.7481   $54.75   $54.75   $54.70  
  Purchase #4 $189.87   11.462%   $211.6329   $211.63   $211.65   $211.60  
  Purchase #5 $239.82   3.216%   $247.5326   $247.53   $247.55   $247.50  
  Purchase #6 $15.68   12.634%   $17.661   $17.66   $17.65   $17.70  
  Purchase #7 $246.70   9.728%   $270.699   $270.70   $270.70   $270.70  
  7 purchase totals = $1,048.83       $1,132.5311   $1,132.53   $1,132.55   $1,132.40