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 $69.26   11.671%   $77.3433   $77.34   $77.35   $77.30  
  Purchase #2 $171.62   8.417%   $186.0653   $186.07   $186.05   $186.10  
  Purchase #3 $161.80   7.718%   $174.2877   $174.29   $174.30   $174.30  
  Purchase #4 $102.59   8.657%   $111.4712   $111.47   $111.45   $111.50  
  Purchase #5 $152.94   4.866%   $160.3821   $160.38   $160.40   $160.40  
  Purchase #6 $67.28   8.433%   $72.9537   $72.95   $72.95   $73.00  
  Purchase #7 $204.26   13.532%   $231.9005   $231.90   $231.90   $231.90  
  7 purchase totals = $929.75       $1,014.4038   $1,014.40   $1,014.40   $1,014.50