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 $44.41   4.421%   $46.3734   $46.37   $46.35   $46.40  
  Purchase #2 $246.80   11.473%   $275.1154   $275.12   $275.10   $275.10  
  Purchase #3 $156.66   11.486%   $174.654   $174.65   $174.65   $174.70  
  Purchase #4 $171.71   10.533%   $189.7962   $189.80   $189.80   $189.80  
  Purchase #5 $206.90   3.841%   $214.847   $214.85   $214.85   $214.80  
  Purchase #6 $202.82   13.556%   $230.3143   $230.31   $230.30   $230.30  
  Purchase #7 $69.97   3.543%   $72.449   $72.45   $72.45   $72.40  
  7 purchase totals = $1,099.27       $1,203.5493   $1,203.55   $1,203.50   $1,203.50