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 $84.44   13.338%   $95.7026   $95.70   $95.70   $95.70  
  Purchase #2 $179.73   12.245%   $201.7379   $201.74   $201.75   $201.70  
  Purchase #3 $134.69   12.172%   $151.0845   $151.08   $151.10   $151.10  
  Purchase #4 $29.55   7.431%   $31.7459   $31.75   $31.75   $31.70  
  Purchase #5 $236.51   7.447%   $254.1229   $254.12   $254.10   $254.10  
  Purchase #6 $50.43   13.682%   $57.3298   $57.33   $57.35   $57.30  
  Purchase #7 $12.39   9.114%   $13.5192   $13.52   $13.50   $13.50  
  7 purchase totals = $727.74       $805.2428   $805.24   $805.25   $805.10