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 $85.95   10.873%   $95.2953   $95.30   $95.30   $95.30  
  Purchase #2 $234.35   9.252%   $256.0321   $256.03   $256.05   $256.00  
  Purchase #3 $227.75   3.293%   $235.2498   $235.25   $235.25   $235.20  
  Purchase #4 $165.27   4.234%   $172.2675   $172.27   $172.25   $172.30  
  Purchase #5 $13.52   11.815%   $15.1174   $15.12   $15.10   $15.10  
  Purchase #6 $67.41   11.537%   $75.1871   $75.19   $75.20   $75.20  
  Purchase #7 $237.81   12.443%   $267.4007   $267.40   $267.40   $267.40  
  7 purchase totals = $1,032.06       $1,116.5499   $1,116.56   $1,116.55   $1,116.50