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 $87.85   11.572%   $98.016   $98.02   $98.00   $98.00  
  Purchase #2 $63.56   6.674%   $67.802   $67.80   $67.80   $67.80  
  Purchase #3 $208.77   8.513%   $226.5426   $226.54   $226.55   $226.50  
  Purchase #4 $197.79   9.208%   $216.0025   $216.00   $216.00   $216.00  
  Purchase #5 $75.37   12.165%   $84.5388   $84.54   $84.55   $84.50  
  Purchase #6 $133.96   6.784%   $143.0478   $143.05   $143.05   $143.00  
  Purchase #7 $26.37   7.324%   $28.3013   $28.30   $28.30   $28.30  
  7 purchase totals = $793.67       $864.2510   $864.25   $864.25   $864.10