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 $225.62   3.792%   $234.1755   $234.18   $234.20   $234.20  
  Purchase #2 $98.30   8.472%   $106.628   $106.63   $106.65   $106.60  
  Purchase #3 $43.86   3.527%   $45.4069   $45.41   $45.40   $45.40  
  Purchase #4 $198.33   5.556%   $209.3492   $209.35   $209.35   $209.30  
  Purchase #5 $38.80   8.584%   $42.1306   $42.13   $42.15   $42.10  
  Purchase #6 $151.53   13.252%   $171.6108   $171.61   $171.60   $171.60  
  Purchase #7 $219.62   7.120%   $235.2569   $235.26   $235.25   $235.30  
  7 purchase totals = $976.06       $1,044.5579   $1,044.57   $1,044.60   $1,044.50