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 $58.57   7.369%   $62.886   $62.89   $62.90   $62.90  
  Purchase #2 $193.32   5.503%   $203.9584   $203.96   $203.95   $204.00  
  Purchase #3 $35.85   8.548%   $38.9145   $38.91   $38.90   $38.90  
  Purchase #4 $246.50   7.703%   $265.4879   $265.49   $265.50   $265.50  
  Purchase #5 $44.64   7.222%   $47.8639   $47.86   $47.85   $47.90  
  Purchase #6 $194.27   6.835%   $207.5484   $207.55   $207.55   $207.50  
  Purchase #7 $161.91   4.120%   $168.5807   $168.58   $168.60   $168.60  
  7 purchase totals = $935.06       $995.2398   $995.24   $995.25   $995.30