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 $44.95   3.581%   $46.5597   $46.56   $46.55   $46.60  
  Purchase #2 $184.58   10.632%   $204.2045   $204.20   $204.20   $204.20  
  Purchase #3 $21.43   6.689%   $22.8635   $22.86   $22.85   $22.90  
  Purchase #4 $35.27   3.102%   $36.3641   $36.36   $36.35   $36.40  
  Purchase #5 $177.35   10.388%   $195.7731   $195.77   $195.75   $195.80  
  Purchase #6 $29.59   11.490%   $32.9899   $32.99   $33.00   $33.00  
  Purchase #7 $239.57   10.194%   $263.9918   $263.99   $264.00   $264.00  
  7 purchase totals = $732.74       $802.7466   $802.73   $802.70   $802.90