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 $49.27   9.330%   $53.8669   $53.87   $53.85   $53.90  
  Purchase #2 $63.27   9.237%   $69.1142   $69.11   $69.10   $69.10  
  Purchase #3 $219.96   11.285%   $244.7825   $244.78   $244.80   $244.80  
  Purchase #4 $248.68   7.688%   $267.7985   $267.80   $267.80   $267.80  
  Purchase #5 $168.70   13.263%   $191.0747   $191.07   $191.05   $191.10  
  Purchase #6 $90.54   8.156%   $97.9244   $97.92   $97.90   $97.90  
  Purchase #7 $201.85   11.360%   $224.7802   $224.78   $224.80   $224.80  
  7 purchase totals = $1,042.27       $1,149.3414   $1,149.33   $1,149.30   $1,149.40