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 $54.74   11.432%   $60.9979   $61.00   $61.00   $61.00  
  Purchase #2 $210.73   3.837%   $218.8157   $218.82   $218.80   $218.80  
  Purchase #3 $77.72   11.507%   $86.6632   $86.66   $86.65   $86.70  
  Purchase #4 $175.71   10.474%   $194.1139   $194.11   $194.10   $194.10  
  Purchase #5 $28.35   7.176%   $30.3844   $30.38   $30.40   $30.40  
  Purchase #6 $227.98   11.285%   $253.7075   $253.71   $253.70   $253.70  
  Purchase #7 $169.96   6.133%   $180.3836   $180.38   $180.40   $180.40  
  7 purchase totals = $945.19       $1,025.0662   $1,025.06   $1,025.05   $1,025.10