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 $196.61   8.349%   $213.025   $213.03   $213.05   $213.00  
  Purchase #2 $207.82   9.859%   $228.309   $228.31   $228.30   $228.30  
  Purchase #3 $226.83   9.375%   $248.0953   $248.10   $248.10   $248.10  
  Purchase #4 $55.97   4.210%   $58.3263   $58.33   $58.35   $58.30  
  Purchase #5 $170.85   13.842%   $194.4991   $194.50   $194.50   $194.50  
  Purchase #6 $221.97   8.427%   $240.6754   $240.68   $240.70   $240.70  
  Purchase #7 $76.97   12.165%   $86.3334   $86.33   $86.35   $86.30  
  7 purchase totals = $1,157.02       $1,269.2635   $1,269.28   $1,269.35   $1,269.20