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 $194.32   3.722%   $201.5526   $201.55   $201.55   $201.60  
  Purchase #2 $226.84   13.432%   $257.3091   $257.31   $257.30   $257.30  
  Purchase #3 $88.57   7.743%   $95.428   $95.43   $95.45   $95.40  
  Purchase #4 $218.63   11.390%   $243.532   $243.53   $243.55   $243.50  
  Purchase #5 $246.30   6.769%   $262.972   $262.97   $262.95   $263.00  
  Purchase #6 $175.32   12.333%   $196.9422   $196.94   $196.95   $196.90  
  Purchase #7 $184.33   7.553%   $198.2524   $198.25   $198.25   $198.30  
  7 purchase totals = $1,334.31       $1,455.9883   $1,455.98   $1,456.00   $1,456.00