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 $49.77   5.561%   $52.5377   $52.54   $52.55   $52.50  
  Purchase #2 $238.89   12.817%   $269.5085   $269.51   $269.50   $269.50  
  Purchase #3 $108.47   6.867%   $115.9186   $115.92   $115.90   $115.90  
  Purchase #4 $177.51   9.524%   $194.4161   $194.42   $194.40   $194.40  
  Purchase #5 $210.86   4.823%   $221.0298   $221.03   $221.05   $221.00  
  Purchase #6 $132.57   8.822%   $144.2653   $144.27   $144.25   $144.30  
  Purchase #7 $108.39   7.294%   $116.296   $116.30   $116.30   $116.30  
  7 purchase totals = $1,026.46       $1,113.9720   $1,113.99   $1,113.95   $1,113.90