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 $175.35   13.644%   $199.2748   $199.27   $199.25   $199.30  
  Purchase #2 $146.84   3.217%   $151.5638   $151.56   $151.55   $151.60  
  Purchase #3 $178.27   3.453%   $184.4257   $184.43   $184.45   $184.40  
  Purchase #4 $200.66   3.658%   $208.0001   $208.00   $208.00   $208.00  
  Purchase #5 $217.31   6.688%   $231.8437   $231.84   $231.85   $231.80  
  Purchase #6 $38.84   4.728%   $40.6764   $40.68   $40.70   $40.70  
  Purchase #7 $104.92   5.581%   $110.7756   $110.78   $110.80   $110.80  
  7 purchase totals = $1,062.19       $1,126.5601   $1,126.56   $1,126.60   $1,126.60