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 $181.38   7.366%   $194.7405   $194.74   $194.75   $194.70  
  Purchase #2 $47.48   8.638%   $51.5813   $51.58   $51.60   $51.60  
  Purchase #3 $41.54   5.408%   $43.7865   $43.79   $43.80   $43.80  
  Purchase #4 $125.83   3.462%   $130.1862   $130.19   $130.20   $130.20  
  Purchase #5 $127.34   3.588%   $131.909   $131.91   $131.90   $131.90  
  Purchase #6 $185.52   12.791%   $209.2499   $209.25   $209.25   $209.20  
  Purchase #7 $172.68   11.279%   $192.1566   $192.16   $192.15   $192.20  
  7 purchase totals = $881.77       $953.6100   $953.62   $953.65   $953.60