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 $39.72   11.201%   $44.169   $44.17   $44.15   $44.20  
  Purchase #2 $113.64   6.655%   $121.2027   $121.20   $121.20   $121.20  
  Purchase #3 $175.38   9.692%   $192.3778   $192.38   $192.40   $192.40  
  Purchase #4 $29.59   6.783%   $31.5971   $31.60   $31.60   $31.60  
  Purchase #5 $154.69   4.303%   $161.3463   $161.35   $161.35   $161.30  
  Purchase #6 $192.31   12.783%   $216.893   $216.89   $216.90   $216.90  
  Purchase #7 $150.28   5.393%   $158.3846   $158.38   $158.40   $158.40  
  7 purchase totals = $855.61       $925.9705   $925.97   $926.00   $926.00