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 $167.27   10.558%   $184.9304   $184.93   $184.95   $184.90  
  Purchase #2 $214.94   10.150%   $236.7564   $236.76   $236.75   $236.80  
  Purchase #3 $226.84   3.592%   $234.9881   $234.99   $235.00   $235.00  
  Purchase #4 $84.79   11.531%   $94.5671   $94.57   $94.55   $94.60  
  Purchase #5 $98.74   7.305%   $105.953   $105.95   $105.95   $106.00  
  Purchase #6 $18.86   9.659%   $20.6817   $20.68   $20.70   $20.70  
  Purchase #7 $222.51   7.608%   $239.4386   $239.44   $239.45   $239.40  
  7 purchase totals = $1,033.95       $1,117.3153   $1,117.32   $1,117.35   $1,117.40