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 $68.51   10.398%   $75.6337   $75.63   $75.65   $75.60  
  Purchase #2 $211.56   7.569%   $227.573   $227.57   $227.55   $227.60  
  Purchase #3 $152.36   5.805%   $161.2045   $161.20   $161.20   $161.20  
  Purchase #4 $54.71   7.394%   $58.7553   $58.76   $58.75   $58.80  
  Purchase #5 $197.90   4.472%   $206.7501   $206.75   $206.75   $206.80  
  Purchase #6 $241.31   7.424%   $259.2249   $259.22   $259.20   $259.20  
  Purchase #7 $65.58   5.528%   $69.2053   $69.21   $69.20   $69.20  
  7 purchase totals = $991.93       $1,058.3468   $1,058.34   $1,058.30   $1,058.40