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 $236.71   10.704%   $262.0474   $262.05   $262.05   $262.00  
  Purchase #2 $204.30   10.290%   $225.3225   $225.32   $225.30   $225.30  
  Purchase #3 $101.43   9.782%   $111.3519   $111.35   $111.35   $111.40  
  Purchase #4 $85.93   11.420%   $95.7432   $95.74   $95.75   $95.70  
  Purchase #5 $161.93   10.609%   $179.1092   $179.11   $179.10   $179.10  
  Purchase #6 $118.25   13.266%   $133.937   $133.94   $133.95   $133.90  
  Purchase #7 $45.98   6.411%   $48.9278   $48.93   $48.95   $48.90  
  7 purchase totals = $954.53       $1,056.4390   $1,056.44   $1,056.45   $1,056.30