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 $43.39   3.593%   $44.949   $44.95   $44.95   $44.90  
  Purchase #2 $207.75   13.740%   $236.2949   $236.29   $236.30   $236.30  
  Purchase #3 $54.79   13.675%   $62.2825   $62.28   $62.30   $62.30  
  Purchase #4 $117.45   5.151%   $123.4998   $123.50   $123.50   $123.50  
  Purchase #5 $66.31   3.825%   $68.8464   $68.85   $68.85   $68.80  
  Purchase #6 $241.49   9.213%   $263.7385   $263.74   $263.75   $263.70  
  Purchase #7 $243.61   12.345%   $273.6837   $273.68   $273.70   $273.70  
  7 purchase totals = $974.79       $1,073.2948   $1,073.29   $1,073.35   $1,073.20