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 $115.27   3.252%   $119.0186   $119.02   $119.00   $119.00  
  Purchase #2 $238.66   12.439%   $268.3469   $268.35   $268.35   $268.30  
  Purchase #3 $96.49   10.134%   $106.2683   $106.27   $106.25   $106.30  
  Purchase #4 $173.46   3.862%   $180.159   $180.16   $180.15   $180.20  
  Purchase #5 $46.50   10.279%   $51.2797   $51.28   $51.30   $51.30  
  Purchase #6 $218.58   12.482%   $245.8632   $245.86   $245.85   $245.90  
  Purchase #7 $196.30   5.274%   $206.6529   $206.65   $206.65   $206.70  
  7 purchase totals = $1,085.26       $1,177.5886   $1,177.59   $1,177.55   $1,177.70