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 $86.97   8.727%   $94.5599   $94.56   $94.55   $94.60  
  Purchase #2 $56.93   3.196%   $58.7495   $58.75   $58.75   $58.70  
  Purchase #3 $113.77   7.399%   $122.1878   $122.19   $122.20   $122.20  
  Purchase #4 $22.47   12.542%   $25.2882   $25.29   $25.30   $25.30  
  Purchase #5 $67.80   6.134%   $71.9589   $71.96   $71.95   $72.00  
  Purchase #6 $165.29   3.372%   $170.8636   $170.86   $170.85   $170.90  
  Purchase #7 $187.70   7.681%   $202.1172   $202.12   $202.10   $202.10  
  7 purchase totals = $700.93       $745.7251   $745.73   $745.70   $745.80