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 $116.58   13.855%   $132.7322   $132.73   $132.75   $132.70  
  Purchase #2 $192.76   5.623%   $203.5989   $203.60   $203.60   $203.60  
  Purchase #3 $174.61   4.270%   $182.0658   $182.07   $182.05   $182.10  
  Purchase #4 $152.30   6.235%   $161.7959   $161.80   $161.80   $161.80  
  Purchase #5 $18.28   5.492%   $19.2839   $19.28   $19.30   $19.30  
  Purchase #6 $155.39   7.815%   $167.5337   $167.53   $167.55   $167.50  
  Purchase #7 $191.74   6.704%   $204.5942   $204.59   $204.60   $204.60  
  7 purchase totals = $1,001.66       $1,071.6046   $1,071.60   $1,071.65   $1,071.60