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 $194.85   3.363%   $201.4028   $201.40   $201.40   $201.40  
  Purchase #2 $58.68   3.188%   $60.5507   $60.55   $60.55   $60.60  
  Purchase #3 $157.77   3.305%   $162.9843   $162.98   $163.00   $163.00  
  Purchase #4 $32.53   9.362%   $35.5755   $35.58   $35.60   $35.60  
  Purchase #5 $53.63   4.383%   $55.9806   $55.98   $56.00   $56.00  
  Purchase #6 $148.59   13.290%   $168.3376   $168.34   $168.35   $168.30  
  Purchase #7 $110.74   13.436%   $125.619   $125.62   $125.60   $125.60  
  7 purchase totals = $756.79       $810.4505   $810.45   $810.50   $810.50