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 $194.27   3.463%   $200.9976   $201.00   $201.00   $201.00  
  Purchase #2 $60.25   6.488%   $64.159   $64.16   $64.15   $64.20  
  Purchase #3 $155.46   7.610%   $167.2905   $167.29   $167.30   $167.30  
  Purchase #4 $195.56   5.629%   $206.5681   $206.57   $206.55   $206.60  
  Purchase #5 $218.65   9.331%   $239.0522   $239.05   $239.05   $239.10  
  Purchase #6 $186.74   8.124%   $201.9108   $201.91   $201.90   $201.90  
  Purchase #7 $22.93   9.841%   $25.1865   $25.19   $25.20   $25.20  
  7 purchase totals = $1,033.86       $1,105.1647   $1,105.17   $1,105.15   $1,105.30