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 $47.36   6.231%   $50.311   $50.31   $50.30   $50.30  
  Purchase #2 $176.87   5.364%   $186.3573   $186.36   $186.35   $186.40  
  Purchase #3 $87.38   10.301%   $96.381   $96.38   $96.40   $96.40  
  Purchase #4 $215.75   7.571%   $232.0844   $232.08   $232.10   $232.10  
  Purchase #5 $143.71   5.158%   $151.1226   $151.12   $151.10   $151.10  
  Purchase #6 $234.29   8.109%   $253.2886   $253.29   $253.30   $253.30  
  Purchase #7 $61.76   3.553%   $63.9543   $63.95   $63.95   $64.00  
  7 purchase totals = $967.12       $1,033.4992   $1,033.49   $1,033.50   $1,033.60