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 $46.28   7.501%   $49.7515   $49.75   $49.75   $49.80  
  Purchase #2 $228.26   3.376%   $235.9661   $235.97   $235.95   $236.00  
  Purchase #3 $75.89   13.272%   $85.9621   $85.96   $85.95   $86.00  
  Purchase #4 $67.54   3.850%   $70.1403   $70.14   $70.15   $70.10  
  Purchase #5 $211.58   8.768%   $230.1313   $230.13   $230.15   $230.10  
  Purchase #6 $250.90   3.766%   $260.3489   $260.35   $260.35   $260.30  
  Purchase #7 $87.83   13.561%   $99.7406   $99.74   $99.75   $99.70  
  7 purchase totals = $968.28       $1,032.0408   $1,032.04   $1,032.05   $1,032.00