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 $195.92   5.245%   $206.196   $206.20   $206.20   $206.20  
  Purchase #2 $147.69   13.335%   $167.3845   $167.38   $167.40   $167.40  
  Purchase #3 $65.75   6.153%   $69.7956   $69.80   $69.80   $69.80  
  Purchase #4 $70.45   5.674%   $74.4473   $74.45   $74.45   $74.40  
  Purchase #5 $248.61   7.559%   $267.4024   $267.40   $267.40   $267.40  
  Purchase #6 $216.92   11.780%   $242.4732   $242.47   $242.45   $242.50  
  Purchase #7 $178.83   11.847%   $200.016   $200.02   $200.00   $200.00  
  7 purchase totals = $1,124.17       $1,227.7150   $1,227.72   $1,227.70   $1,227.70