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 $60.77   13.554%   $69.0068   $69.01   $69.00   $69.00  
  Purchase #2 $116.30   9.751%   $127.6404   $127.64   $127.65   $127.60  
  Purchase #3 $39.48   10.422%   $43.5946   $43.59   $43.60   $43.60  
  Purchase #4 $102.90   3.729%   $106.7371   $106.74   $106.75   $106.70  
  Purchase #5 $102.46   5.230%   $107.8187   $107.82   $107.80   $107.80  
  Purchase #6 $248.64   8.102%   $268.7848   $268.78   $268.80   $268.80  
  Purchase #7 $118.56   10.401%   $130.8914   $130.89   $130.90   $130.90  
  7 purchase totals = $789.11       $854.4738   $854.47   $854.50   $854.40