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 $201.57   5.681%   $213.0212   $213.02   $213.00   $213.00  
  Purchase #2 $208.91   12.837%   $235.7278   $235.73   $235.75   $235.70  
  Purchase #3 $186.99   10.194%   $206.0518   $206.05   $206.05   $206.10  
  Purchase #4 $57.80   4.613%   $60.4663   $60.47   $60.45   $60.50  
  Purchase #5 $167.90   9.313%   $183.5365   $183.54   $183.55   $183.50  
  Purchase #6 $219.82   4.349%   $229.38   $229.38   $229.40   $229.40  
  Purchase #7 $75.86   5.123%   $79.7463   $79.75   $79.75   $79.70  
  7 purchase totals = $1,118.85       $1,207.9299   $1,207.94   $1,207.95   $1,207.90