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 $181.83   10.664%   $201.2204   $201.22   $201.20   $201.20  
  Purchase #2 $63.46   13.202%   $71.838   $71.84   $71.85   $71.80  
  Purchase #3 $153.81   11.405%   $171.352   $171.35   $171.35   $171.40  
  Purchase #4 $80.71   5.544%   $85.1846   $85.18   $85.20   $85.20  
  Purchase #5 $141.59   6.825%   $151.2535   $151.25   $151.25   $151.30  
  Purchase #6 $187.61   7.575%   $201.8215   $201.82   $201.80   $201.80  
  Purchase #7 $46.34   6.370%   $49.2919   $49.29   $49.30   $49.30  
  7 purchase totals = $855.35       $931.9619   $931.95   $931.95   $932.00