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 $233.85   10.157%   $257.6021   $257.60   $257.60   $257.60  
  Purchase #2 $89.97   8.463%   $97.5842   $97.58   $97.60   $97.60  
  Purchase #3 $175.57   5.573%   $185.3545   $185.35   $185.35   $185.40  
  Purchase #4 $34.75   9.385%   $38.0113   $38.01   $38.00   $38.00  
  Purchase #5 $165.56   11.255%   $184.1938   $184.19   $184.20   $184.20  
  Purchase #6 $54.25   7.550%   $58.3459   $58.35   $58.35   $58.30  
  Purchase #7 $219.53   9.373%   $240.1065   $240.11   $240.10   $240.10  
  7 purchase totals = $973.48       $1,061.1983   $1,061.19   $1,061.20   $1,061.20