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 $214.94   12.848%   $242.5555   $242.56   $242.55   $242.60  
  Purchase #2 $244.54   7.132%   $261.9806   $261.98   $262.00   $262.00  
  Purchase #3 $240.56   9.754%   $264.0242   $264.02   $264.00   $264.00  
  Purchase #4 $162.43   12.490%   $182.7175   $182.72   $182.70   $182.70  
  Purchase #5 $56.60   13.700%   $64.3542   $64.35   $64.35   $64.40  
  Purchase #6 $221.94   10.826%   $245.9672   $245.97   $245.95   $246.00  
  Purchase #7 $187.49   10.682%   $207.5177   $207.52   $207.50   $207.50  
  7 purchase totals = $1,328.50       $1,469.1169   $1,469.12   $1,469.05   $1,469.20