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 $110.96   7.513%   $119.2964   $119.30   $119.30   $119.30  
  Purchase #2 $144.31   4.168%   $150.3248   $150.32   $150.30   $150.30  
  Purchase #3 $123.99   8.566%   $134.611   $134.61   $134.60   $134.60  
  Purchase #4 $42.54   6.830%   $45.4455   $45.45   $45.45   $45.40  
  Purchase #5 $52.75   7.236%   $56.567   $56.57   $56.55   $56.60  
  Purchase #6 $121.74   8.603%   $132.2133   $132.21   $132.20   $132.20  
  Purchase #7 $225.47   5.381%   $237.6025   $237.60   $237.60   $237.60  
  7 purchase totals = $821.76       $876.0605   $876.06   $876.00   $876.00