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 $115.81   9.106%   $126.3557   $126.36   $126.35   $126.40  
  Purchase #2 $229.64   3.572%   $237.8427   $237.84   $237.85   $237.80  
  Purchase #3 $44.58   13.847%   $50.753   $50.75   $50.75   $50.80  
  Purchase #4 $191.81   5.785%   $202.9062   $202.91   $202.90   $202.90  
  Purchase #5 $212.92   7.546%   $228.9869   $228.99   $229.00   $229.00  
  Purchase #6 $58.48   7.396%   $62.8052   $62.81   $62.80   $62.80  
  Purchase #7 $191.69   5.191%   $201.6406   $201.64   $201.65   $201.60  
  7 purchase totals = $1,044.93       $1,111.2903   $1,111.30   $1,111.30   $1,111.30