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 $161.73   12.696%   $182.2632   $182.26   $182.25   $182.30  
  Purchase #2 $43.39   6.586%   $46.2477   $46.25   $46.25   $46.20  
  Purchase #3 $172.30   12.692%   $194.1683   $194.17   $194.15   $194.20  
  Purchase #4 $142.29   3.367%   $147.0809   $147.08   $147.10   $147.10  
  Purchase #5 $133.33   11.252%   $148.3323   $148.33   $148.35   $148.30  
  Purchase #6 $245.40   4.499%   $256.4405   $256.44   $256.45   $256.40  
  Purchase #7 $219.60   5.771%   $232.2731   $232.27   $232.25   $232.30  
  7 purchase totals = $1,118.04       $1,206.8060   $1,206.80   $1,206.80   $1,206.80