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 $38.98   5.595%   $41.1609   $41.16   $41.15   $41.20  
  Purchase #2 $118.73   6.713%   $126.7003   $126.70   $126.70   $126.70  
  Purchase #3 $30.56   11.154%   $33.9687   $33.97   $33.95   $34.00  
  Purchase #4 $201.45   12.865%   $227.3665   $227.37   $227.35   $227.40  
  Purchase #5 $204.91   8.530%   $222.3888   $222.39   $222.40   $222.40  
  Purchase #6 $243.43   4.533%   $254.4647   $254.46   $254.45   $254.50  
  Purchase #7 $226.80   8.734%   $246.6087   $246.61   $246.60   $246.60  
  7 purchase totals = $1,064.86       $1,152.6586   $1,152.66   $1,152.60   $1,152.80