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 $182.26   10.121%   $200.7065   $200.71   $200.70   $200.70  
  Purchase #2 $149.83   11.433%   $166.9601   $166.96   $166.95   $167.00  
  Purchase #3 $96.29   5.173%   $101.2711   $101.27   $101.25   $101.30  
  Purchase #4 $172.78   4.751%   $180.9888   $180.99   $181.00   $181.00  
  Purchase #5 $54.37   11.261%   $60.4926   $60.49   $60.50   $60.50  
  Purchase #6 $228.77   3.567%   $236.9302   $236.93   $236.95   $236.90  
  Purchase #7 $173.60   7.130%   $185.9777   $185.98   $186.00   $186.00  
  7 purchase totals = $1,057.90       $1,133.3270   $1,133.33   $1,133.35   $1,133.40