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 $72.27   3.293%   $74.6499   $74.65   $74.65   $74.60  
  Purchase #2 $230.71   4.348%   $240.7413   $240.74   $240.75   $240.70  
  Purchase #3 $17.40   5.569%   $18.369   $18.37   $18.35   $18.40  
  Purchase #4 $155.59   12.344%   $174.796   $174.80   $174.80   $174.80  
  Purchase #5 $236.84   6.164%   $251.4388   $251.44   $251.45   $251.40  
  Purchase #6 $121.92   12.751%   $137.466   $137.47   $137.45   $137.50  
  Purchase #7 $111.74   4.694%   $116.9851   $116.99   $117.00   $117.00  
  7 purchase totals = $946.47       $1,014.4461   $1,014.46   $1,014.45   $1,014.40