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 $168.26   8.276%   $182.1852   $182.19   $182.20   $182.20  
  Purchase #2 $195.65   8.578%   $212.4329   $212.43   $212.45   $212.40  
  Purchase #3 $52.78   6.437%   $56.1774   $56.18   $56.20   $56.20  
  Purchase #4 $238.43   5.186%   $250.795   $250.80   $250.80   $250.80  
  Purchase #5 $32.41   9.438%   $35.4689   $35.47   $35.45   $35.50  
  Purchase #6 $223.36   9.851%   $245.3632   $245.36   $245.35   $245.40  
  Purchase #7 $218.33   11.683%   $243.8375   $243.84   $243.85   $243.80  
  7 purchase totals = $1,129.22       $1,226.2601   $1,226.27   $1,226.30   $1,226.30