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 $119.87   4.482%   $125.2426   $125.24   $125.25   $125.20  
  Purchase #2 $213.80   8.520%   $232.0158   $232.02   $232.00   $232.00  
  Purchase #3 $218.29   8.360%   $236.539   $236.54   $236.55   $236.50  
  Purchase #4 $189.72   7.259%   $203.4918   $203.49   $203.50   $203.50  
  Purchase #5 $114.28   12.532%   $128.6016   $128.60   $128.60   $128.60  
  Purchase #6 $147.64   8.607%   $160.3474   $160.35   $160.35   $160.30  
  Purchase #7 $21.31   13.842%   $24.2597   $24.26   $24.25   $24.30  
  7 purchase totals = $1,024.91       $1,110.4979   $1,110.50   $1,110.50   $1,110.40