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 $87.81   8.612%   $95.3722   $95.37   $95.35   $95.40  
  Purchase #2 $193.62   13.704%   $220.1537   $220.15   $220.15   $220.20  
  Purchase #3 $28.37   13.281%   $32.1378   $32.14   $32.15   $32.10  
  Purchase #4 $243.37   6.842%   $260.0214   $260.02   $260.00   $260.00  
  Purchase #5 $229.58   11.502%   $255.9863   $255.99   $256.00   $256.00  
  Purchase #6 $156.56   5.508%   $165.1833   $165.18   $165.20   $165.20  
  Purchase #7 $29.71   13.471%   $33.7122   $33.71   $33.70   $33.70  
  7 purchase totals = $969.02       $1,062.5669   $1,062.56   $1,062.55   $1,062.60