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 $195.98   6.771%   $209.2498   $209.25   $209.25   $209.20  
  Purchase #2 $168.55   6.603%   $179.6794   $179.68   $179.70   $179.70  
  Purchase #3 $243.59   5.277%   $256.4442   $256.44   $256.45   $256.40  
  Purchase #4 $35.78   10.643%   $39.5881   $39.59   $39.60   $39.60  
  Purchase #5 $99.60   5.759%   $105.336   $105.34   $105.35   $105.30  
  Purchase #6 $171.49   13.504%   $194.648   $194.65   $194.65   $194.60  
  Purchase #7 $129.77   3.311%   $134.0667   $134.07   $134.05   $134.10  
  7 purchase totals = $1,044.76       $1,119.0122   $1,119.02   $1,119.05   $1,118.90