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 $106.41   5.251%   $111.9976   $112.00   $112.00   $112.00  
  Purchase #2 $225.37   3.726%   $233.7673   $233.77   $233.75   $233.80  
  Purchase #3 $134.59   9.316%   $147.1284   $147.13   $147.15   $147.10  
  Purchase #4 $52.63   11.315%   $58.5851   $58.59   $58.60   $58.60  
  Purchase #5 $177.30   3.423%   $183.369   $183.37   $183.35   $183.40  
  Purchase #6 $147.30   6.503%   $156.8789   $156.88   $156.90   $156.90  
  Purchase #7 $216.79   11.436%   $241.5821   $241.58   $241.60   $241.60  
  7 purchase totals = $1,060.39       $1,133.3084   $1,133.32   $1,133.35   $1,133.40