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 $41.78   3.775%   $43.3572   $43.36   $43.35   $43.40  
  Purchase #2 $86.60   5.812%   $91.6332   $91.63   $91.65   $91.60  
  Purchase #3 $44.51   5.407%   $46.9167   $46.92   $46.90   $46.90  
  Purchase #4 $215.47   8.154%   $233.0394   $233.04   $233.05   $233.00  
  Purchase #5 $22.37   7.851%   $24.1263   $24.13   $24.15   $24.10  
  Purchase #6 $190.66   3.642%   $197.6038   $197.60   $197.60   $197.60  
  Purchase #7 $91.88   4.824%   $96.3123   $96.31   $96.30   $96.30  
  7 purchase totals = $693.27       $732.9889   $732.99   $733.00   $732.90