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 $86.30   8.139%   $93.324   $93.32   $93.30   $93.30  
  Purchase #2 $186.25   6.284%   $197.954   $197.95   $197.95   $198.00  
  Purchase #3 $233.99   5.502%   $246.8641   $246.86   $246.85   $246.90  
  Purchase #4 $219.84   12.784%   $247.9443   $247.94   $247.95   $247.90  
  Purchase #5 $82.51   5.378%   $86.9474   $86.95   $86.95   $86.90  
  Purchase #6 $196.39   8.669%   $213.415   $213.42   $213.40   $213.40  
  Purchase #7 $22.68   11.535%   $25.2961   $25.30   $25.30   $25.30  
  7 purchase totals = $1,027.96       $1,111.7449   $1,111.74   $1,111.70   $1,111.70