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 $200.94   8.137%   $217.2905   $217.29   $217.30   $217.30  
  Purchase #2 $118.51   6.522%   $126.2392   $126.24   $126.25   $126.20  
  Purchase #3 $197.86   13.681%   $224.9292   $224.93   $224.95   $224.90  
  Purchase #4 $134.67   3.147%   $138.9081   $138.91   $138.90   $138.90  
  Purchase #5 $166.78   3.460%   $172.5506   $172.55   $172.55   $172.60  
  Purchase #6 $135.60   10.322%   $149.5966   $149.60   $149.60   $149.60  
  Purchase #7 $112.75   8.250%   $122.0519   $122.05   $122.05   $122.10  
  7 purchase totals = $1,067.11       $1,151.5661   $1,151.57   $1,151.60   $1,151.60