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 $174.46   12.188%   $195.7232   $195.72   $195.70   $195.70  
  Purchase #2 $46.43   4.178%   $48.3698   $48.37   $48.35   $48.40  
  Purchase #3 $156.48   12.162%   $175.5111   $175.51   $175.50   $175.50  
  Purchase #4 $220.31   10.435%   $243.2993   $243.30   $243.30   $243.30  
  Purchase #5 $91.90   7.157%   $98.4773   $98.48   $98.50   $98.50  
  Purchase #6 $126.83   13.617%   $144.1004   $144.10   $144.10   $144.10  
  Purchase #7 $219.45   11.336%   $244.3269   $244.33   $244.35   $244.30  
  7 purchase totals = $1,035.86       $1,149.8080   $1,149.81   $1,149.80   $1,149.80