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 $209.60   11.155%   $232.9809   $232.98   $233.00   $233.00  
  Purchase #2 $41.69   4.753%   $43.6715   $43.67   $43.65   $43.70  
  Purchase #3 $95.50   6.223%   $101.443   $101.44   $101.45   $101.40  
  Purchase #4 $155.51   13.874%   $177.0855   $177.09   $177.10   $177.10  
  Purchase #5 $210.64   3.848%   $218.7454   $218.75   $218.75   $218.70  
  Purchase #6 $37.93   10.479%   $41.9047   $41.90   $41.90   $41.90  
  Purchase #7 $245.25   6.453%   $261.076   $261.08   $261.10   $261.10  
  7 purchase totals = $996.12       $1,076.9070   $1,076.91   $1,076.95   $1,076.90