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 $174.81   12.128%   $196.011   $196.01   $196.00   $196.00  
  Purchase #2 $35.29   4.425%   $36.8516   $36.85   $36.85   $36.90  
  Purchase #3 $241.46   7.779%   $260.2432   $260.24   $260.25   $260.20  
  Purchase #4 $51.53   10.419%   $56.8989   $56.90   $56.90   $56.90  
  Purchase #5 $246.41   3.426%   $254.852   $254.85   $254.85   $254.90  
  Purchase #6 $40.73   12.635%   $45.8762   $45.88   $45.90   $45.90  
  Purchase #7 $188.82   6.638%   $201.3539   $201.35   $201.35   $201.40  
  7 purchase totals = $979.05       $1,052.0868   $1,052.08   $1,052.10   $1,052.20