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 $82.53   5.593%   $87.1459   $87.15   $87.15   $87.10  
  Purchase #2 $247.32   8.284%   $267.808   $267.81   $267.80   $267.80  
  Purchase #3 $53.40   3.416%   $55.2241   $55.22   $55.20   $55.20  
  Purchase #4 $73.45   13.251%   $83.1829   $83.18   $83.20   $83.20  
  Purchase #5 $151.26   3.535%   $156.607   $156.61   $156.60   $156.60  
  Purchase #6 $234.53   4.826%   $245.8484   $245.85   $245.85   $245.80  
  Purchase #7 $104.63   11.394%   $116.5515   $116.55   $116.55   $116.60  
  7 purchase totals = $947.12       $1,012.3678   $1,012.37   $1,012.35   $1,012.30