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 $33.51   11.200%   $37.2631   $37.26   $37.25   $37.30  
  Purchase #2 $180.89   9.230%   $197.5861   $197.59   $197.60   $197.60  
  Purchase #3 $182.77   8.810%   $198.872   $198.87   $198.85   $198.90  
  Purchase #4 $65.35   11.474%   $72.8483   $72.85   $72.85   $72.80  
  Purchase #5 $192.27   7.270%   $206.248   $206.25   $206.25   $206.20  
  Purchase #6 $142.69   6.524%   $151.9991   $152.00   $152.00   $152.00  
  Purchase #7 $247.78   9.618%   $271.6115   $271.61   $271.60   $271.60  
  7 purchase totals = $1,045.26       $1,136.4281   $1,136.43   $1,136.40   $1,136.40