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 $95.90   5.368%   $101.0479   $101.05   $101.05   $101.00  
  Purchase #2 $206.31   4.419%   $215.4268   $215.43   $215.45   $215.40  
  Purchase #3 $104.86   11.715%   $117.1443   $117.14   $117.15   $117.10  
  Purchase #4 $197.85   8.434%   $214.5367   $214.54   $214.55   $214.50  
  Purchase #5 $87.25   8.545%   $94.7055   $94.71   $94.70   $94.70  
  Purchase #6 $105.25   9.494%   $115.2424   $115.24   $115.25   $115.20  
  Purchase #7 $216.43   12.413%   $243.2955   $243.30   $243.30   $243.30  
  7 purchase totals = $1,013.85       $1,101.3991   $1,101.41   $1,101.45   $1,101.20