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 $195.52   10.864%   $216.7613   $216.76   $216.75   $216.80  
  Purchase #2 $218.41   7.402%   $234.5767   $234.58   $234.60   $234.60  
  Purchase #3 $157.86   8.148%   $170.7224   $170.72   $170.70   $170.70  
  Purchase #4 $62.72   11.682%   $70.047   $70.05   $70.05   $70.00  
  Purchase #5 $41.92   6.161%   $44.5027   $44.50   $44.50   $44.50  
  Purchase #6 $229.67   3.838%   $238.4847   $238.48   $238.50   $238.50  
  Purchase #7 $60.29   10.784%   $66.7917   $66.79   $66.80   $66.80  
  7 purchase totals = $966.39       $1,041.8865   $1,041.88   $1,041.90   $1,041.90