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 $118.58   4.273%   $123.6469   $123.65   $123.65   $123.60  
  Purchase #2 $52.99   3.284%   $54.7302   $54.73   $54.75   $54.70  
  Purchase #3 $114.81   4.180%   $119.6091   $119.61   $119.60   $119.60  
  Purchase #4 $198.41   11.604%   $221.4335   $221.43   $221.45   $221.40  
  Purchase #5 $168.54   7.572%   $181.3018   $181.30   $181.30   $181.30  
  Purchase #6 $234.67   5.173%   $246.8095   $246.81   $246.80   $246.80  
  Purchase #7 $88.86   10.144%   $97.874   $97.87   $97.85   $97.90  
  7 purchase totals = $976.86       $1,045.4050   $1,045.40   $1,045.40   $1,045.30