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 $177.27   3.304%   $183.127   $183.13   $183.15   $183.10  
  Purchase #2 $217.51   5.684%   $229.8733   $229.87   $229.85   $229.90  
  Purchase #3 $76.91   13.826%   $87.5436   $87.54   $87.55   $87.50  
  Purchase #4 $217.35   3.233%   $224.3769   $224.38   $224.40   $224.40  
  Purchase #5 $59.65   3.834%   $61.937   $61.94   $61.95   $61.90  
  Purchase #6 $97.79   4.598%   $102.2864   $102.29   $102.30   $102.30  
  Purchase #7 $202.55   7.375%   $217.4881   $217.49   $217.50   $217.50  
  7 purchase totals = $1,049.03       $1,106.6323   $1,106.64   $1,106.70   $1,106.60