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 $64.90   5.592%   $68.5292   $68.53   $68.55   $68.50  
  Purchase #2 $191.83   9.340%   $209.7469   $209.75   $209.75   $209.70  
  Purchase #3 $98.42   4.629%   $102.9759   $102.98   $103.00   $103.00  
  Purchase #4 $212.33   3.208%   $219.1415   $219.14   $219.15   $219.10  
  Purchase #5 $231.48   13.247%   $262.1442   $262.14   $262.15   $262.10  
  Purchase #6 $236.48   10.160%   $260.5064   $260.51   $260.50   $260.50  
  Purchase #7 $191.70   10.501%   $211.8304   $211.83   $211.85   $211.80  
  7 purchase totals = $1,227.14       $1,334.8745   $1,334.88   $1,334.95   $1,334.70