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 $85.29   11.506%   $95.1035   $95.10   $95.10   $95.10  
  Purchase #2 $86.68   13.158%   $98.0854   $98.09   $98.10   $98.10  
  Purchase #3 $158.36   11.511%   $176.5888   $176.59   $176.60   $176.60  
  Purchase #4 $61.95   8.451%   $67.1854   $67.19   $67.20   $67.20  
  Purchase #5 $202.89   12.454%   $228.1579   $228.16   $228.15   $228.20  
  Purchase #6 $231.57   7.594%   $249.1554   $249.16   $249.15   $249.20  
  Purchase #7 $209.96   7.276%   $225.2367   $225.24   $225.25   $225.20  
  7 purchase totals = $1,036.70       $1,139.5131   $1,139.53   $1,139.55   $1,139.60