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 $47.90   11.152%   $53.2418   $53.24   $53.25   $53.20  
  Purchase #2 $174.54   9.356%   $190.87   $190.87   $190.85   $190.90  
  Purchase #3 $185.78   8.185%   $200.9861   $200.99   $201.00   $201.00  
  Purchase #4 $224.84   10.336%   $248.0795   $248.08   $248.10   $248.10  
  Purchase #5 $212.93   10.384%   $235.0407   $235.04   $235.05   $235.00  
  Purchase #6 $170.81   13.741%   $194.281   $194.28   $194.30   $194.30  
  Purchase #7 $67.50   7.854%   $72.8015   $72.80   $72.80   $72.80  
  7 purchase totals = $1,084.30       $1,195.3006   $1,195.30   $1,195.35   $1,195.30