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 $142.49   7.256%   $152.8291   $152.83   $152.85   $152.80  
  Purchase #2 $101.97   7.269%   $109.3822   $109.38   $109.40   $109.40  
  Purchase #3 $136.72   5.289%   $143.9511   $143.95   $143.95   $144.00  
  Purchase #4 $31.28   13.826%   $35.6048   $35.60   $35.60   $35.60  
  Purchase #5 $228.28   4.201%   $237.87   $237.87   $237.85   $237.90  
  Purchase #6 $167.67   8.191%   $181.4038   $181.40   $181.40   $181.40  
  Purchase #7 $178.35   12.697%   $200.9951   $201.00   $201.00   $201.00  
  7 purchase totals = $986.76       $1,062.0361   $1,062.03   $1,062.05   $1,062.10