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 $29.55   11.603%   $32.9787   $32.98   $33.00   $33.00  
  Purchase #2 $53.91   11.817%   $60.2805   $60.28   $60.30   $60.30  
  Purchase #3 $196.78   5.530%   $207.6619   $207.66   $207.65   $207.70  
  Purchase #4 $150.98   11.833%   $168.8455   $168.85   $168.85   $168.80  
  Purchase #5 $203.29   5.283%   $214.0298   $214.03   $214.05   $214.00  
  Purchase #6 $201.63   12.425%   $226.6825   $226.68   $226.70   $226.70  
  Purchase #7 $138.55   10.523%   $153.1296   $153.13   $153.15   $153.10  
  7 purchase totals = $974.69       $1,063.6085   $1,063.61   $1,063.70   $1,063.60