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 $197.25   6.568%   $210.2054   $210.21   $210.20   $210.20  
  Purchase #2 $66.64   5.490%   $70.2985   $70.30   $70.30   $70.30  
  Purchase #3 $216.39   4.535%   $226.2033   $226.20   $226.20   $226.20  
  Purchase #4 $225.60   6.596%   $240.4806   $240.48   $240.50   $240.50  
  Purchase #5 $108.87   10.545%   $120.3503   $120.35   $120.35   $120.40  
  Purchase #6 $120.62   3.532%   $124.8803   $124.88   $124.90   $124.90  
  Purchase #7 $158.28   5.479%   $166.9522   $166.95   $166.95   $167.00  
  7 purchase totals = $1,093.65       $1,159.3706   $1,159.37   $1,159.40   $1,159.50