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 $62.49   8.107%   $67.5561   $67.56   $67.55   $67.60  
  Purchase #2 $32.39   4.527%   $33.8563   $33.86   $33.85   $33.90  
  Purchase #3 $108.35   11.273%   $120.5643   $120.56   $120.55   $120.60  
  Purchase #4 $197.59   9.350%   $216.0647   $216.06   $216.05   $216.10  
  Purchase #5 $228.83   11.360%   $254.8251   $254.83   $254.85   $254.80  
  Purchase #6 $44.50   6.540%   $47.4103   $47.41   $47.40   $47.40  
  Purchase #7 $158.48   11.290%   $176.3724   $176.37   $176.35   $176.40  
  7 purchase totals = $832.63       $916.6492   $916.65   $916.60   $916.80