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 $32.86   5.189%   $34.5651   $34.57   $34.55   $34.60  
  Purchase #2 $97.26   8.266%   $105.2995   $105.30   $105.30   $105.30  
  Purchase #3 $214.67   13.589%   $243.8415   $243.84   $243.85   $243.80  
  Purchase #4 $167.45   5.865%   $177.2709   $177.27   $177.25   $177.30  
  Purchase #5 $172.99   7.343%   $185.6927   $185.69   $185.70   $185.70  
  Purchase #6 $47.62   12.628%   $53.6335   $53.63   $53.65   $53.60  
  Purchase #7 $194.94   5.263%   $205.1997   $205.20   $205.20   $205.20  
  7 purchase totals = $927.79       $1,005.5029   $1,005.50   $1,005.50   $1,005.50