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 $190.61   5.267%   $200.6494   $200.65   $200.65   $200.60  
  Purchase #2 $22.46   6.670%   $23.9581   $23.96   $23.95   $24.00  
  Purchase #3 $153.29   9.126%   $167.2792   $167.28   $167.30   $167.30  
  Purchase #4 $91.32   8.710%   $99.274   $99.27   $99.25   $99.30  
  Purchase #5 $217.87   13.509%   $247.3021   $247.30   $247.30   $247.30  
  Purchase #6 $247.41   11.561%   $276.0131   $276.01   $276.00   $276.00  
  Purchase #7 $229.60   9.198%   $250.7186   $250.72   $250.70   $250.70  
  7 purchase totals = $1,152.56       $1,265.1945   $1,265.19   $1,265.15   $1,265.20