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 $164.42   10.836%   $182.2366   $182.24   $182.25   $182.20  
  Purchase #2 $54.71   5.766%   $57.8646   $57.86   $57.85   $57.90  
  Purchase #3 $210.42   7.831%   $226.898   $226.90   $226.90   $226.90  
  Purchase #4 $191.94   6.188%   $203.8172   $203.82   $203.80   $203.80  
  Purchase #5 $201.26   11.810%   $225.0288   $225.03   $225.05   $225.00  
  Purchase #6 $65.43   13.294%   $74.1283   $74.13   $74.15   $74.10  
  Purchase #7 $206.31   9.688%   $226.2973   $226.30   $226.30   $226.30  
  7 purchase totals = $1,094.49       $1,196.2708   $1,196.28   $1,196.30   $1,196.20