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 $141.25   8.315%   $152.9949   $152.99   $153.00   $153.00  
  Purchase #2 $237.92   13.382%   $269.7585   $269.76   $269.75   $269.80  
  Purchase #3 $200.51   7.176%   $214.8986   $214.90   $214.90   $214.90  
  Purchase #4 $58.51   8.222%   $63.3207   $63.32   $63.30   $63.30  
  Purchase #5 $60.56   9.156%   $66.1049   $66.10   $66.10   $66.10  
  Purchase #6 $94.72   6.650%   $101.0189   $101.02   $101.00   $101.00  
  Purchase #7 $147.67   13.209%   $167.1757   $167.18   $167.20   $167.20  
  7 purchase totals = $941.14       $1,035.2722   $1,035.27   $1,035.25   $1,035.30