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 $44.44   6.573%   $47.361   $47.36   $47.35   $47.40  
  Purchase #2 $167.62   9.409%   $183.3914   $183.39   $183.40   $183.40  
  Purchase #3 $71.86   4.245%   $74.9105   $74.91   $74.90   $74.90  
  Purchase #4 $146.99   3.505%   $152.142   $152.14   $152.15   $152.10  
  Purchase #5 $215.69   3.470%   $223.1744   $223.17   $223.15   $223.20  
  Purchase #6 $203.52   6.522%   $216.7936   $216.79   $216.80   $216.80  
  Purchase #7 $224.96   4.480%   $235.0382   $235.04   $235.05   $235.00  
  7 purchase totals = $1,075.08       $1,132.8111   $1,132.80   $1,132.80   $1,132.80