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 $57.53   5.501%   $60.6947   $60.69   $60.70   $60.70  
  Purchase #2 $132.54   3.518%   $137.2028   $137.20   $137.20   $137.20  
  Purchase #3 $246.60   3.188%   $254.4616   $254.46   $254.45   $254.50  
  Purchase #4 $67.32   10.398%   $74.3199   $74.32   $74.30   $74.30  
  Purchase #5 $232.27   12.599%   $261.5337   $261.53   $261.55   $261.50  
  Purchase #6 $119.68   5.250%   $125.9632   $125.96   $125.95   $126.00  
  Purchase #7 $120.55   12.708%   $135.8695   $135.87   $135.85   $135.90  
  7 purchase totals = $976.49       $1,050.0454   $1,050.03   $1,050.00   $1,050.10