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 $195.41   5.842%   $206.8259   $206.83   $206.85   $206.80  
  Purchase #2 $51.26   6.570%   $54.6278   $54.63   $54.65   $54.60  
  Purchase #3 $157.30   11.571%   $175.5012   $175.50   $175.50   $175.50  
  Purchase #4 $61.73   8.679%   $67.0875   $67.09   $67.10   $67.10  
  Purchase #5 $82.54   7.484%   $88.7173   $88.72   $88.70   $88.70  
  Purchase #6 $190.32   3.629%   $197.2267   $197.23   $197.25   $197.20  
  Purchase #7 $209.26   7.618%   $225.2014   $225.20   $225.20   $225.20  
  7 purchase totals = $947.82       $1,015.1878   $1,015.20   $1,015.25   $1,015.10