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 $237.56   10.116%   $261.5916   $261.59   $261.60   $261.60  
  Purchase #2 $194.52   7.694%   $209.4864   $209.49   $209.50   $209.50  
  Purchase #3 $173.26   8.710%   $188.3509   $188.35   $188.35   $188.40  
  Purchase #4 $13.82   7.592%   $14.8692   $14.87   $14.85   $14.90  
  Purchase #5 $231.57   6.534%   $246.7008   $246.70   $246.70   $246.70  
  Purchase #6 $49.90   9.723%   $54.7518   $54.75   $54.75   $54.80  
  Purchase #7 $46.74   4.300%   $48.7498   $48.75   $48.75   $48.70  
  7 purchase totals = $947.37       $1,024.5005   $1,024.50   $1,024.50   $1,024.60