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 $145.53   7.417%   $156.324   $156.32   $156.30   $156.30  
  Purchase #2 $108.66   7.263%   $116.552   $116.55   $116.55   $116.60  
  Purchase #3 $212.81   9.233%   $232.4587   $232.46   $232.45   $232.50  
  Purchase #4 $247.89   8.500%   $268.9607   $268.96   $268.95   $269.00  
  Purchase #5 $116.51   7.506%   $125.2552   $125.26   $125.25   $125.30  
  Purchase #6 $22.57   6.155%   $23.9592   $23.96   $23.95   $24.00  
  Purchase #7 $182.51   4.428%   $190.5915   $190.59   $190.60   $190.60  
  7 purchase totals = $1,036.48       $1,114.1013   $1,114.10   $1,114.05   $1,114.30