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 $90.67   3.302%   $93.6639   $93.66   $93.65   $93.70  
  Purchase #2 $169.26   4.327%   $176.5839   $176.58   $176.60   $176.60  
  Purchase #3 $185.95   4.444%   $194.2136   $194.21   $194.20   $194.20  
  Purchase #4 $25.33   6.522%   $26.982   $26.98   $27.00   $27.00  
  Purchase #5 $19.53   11.234%   $21.724   $21.72   $21.70   $21.70  
  Purchase #6 $35.75   4.315%   $37.2926   $37.29   $37.30   $37.30  
  Purchase #7 $162.46   7.208%   $174.1701   $174.17   $174.15   $174.20  
  7 purchase totals = $688.95       $724.6301   $724.61   $724.60   $724.70