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 $246.95   6.120%   $262.0633   $262.06   $262.05   $262.10  
  Purchase #2 $92.71   6.495%   $98.7315   $98.73   $98.75   $98.70  
  Purchase #3 $202.68   11.447%   $225.8808   $225.88   $225.90   $225.90  
  Purchase #4 $219.67   5.140%   $230.961   $230.96   $230.95   $231.00  
  Purchase #5 $147.51   13.676%   $167.6835   $167.68   $167.70   $167.70  
  Purchase #6 $85.39   11.540%   $95.244   $95.24   $95.25   $95.20  
  Purchase #7 $113.32   6.655%   $120.8614   $120.86   $120.85   $120.90  
  7 purchase totals = $1,108.23       $1,201.4255   $1,201.41   $1,201.45   $1,201.50