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 $41.36   4.106%   $43.0582   $43.06   $43.05   $43.10  
  Purchase #2 $137.43   10.576%   $151.9646   $151.96   $151.95   $152.00  
  Purchase #3 $141.63   13.777%   $161.1424   $161.14   $161.15   $161.10  
  Purchase #4 $167.63   4.601%   $175.3427   $175.34   $175.35   $175.30  
  Purchase #5 $124.25   9.160%   $135.6313   $135.63   $135.65   $135.60  
  Purchase #6 $236.97   3.321%   $244.8398   $244.84   $244.85   $244.80  
  Purchase #7 $226.30   3.436%   $234.0757   $234.08   $234.10   $234.10  
  7 purchase totals = $1,075.57       $1,146.0547   $1,146.05   $1,146.10   $1,146.00