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 $193.86   3.633%   $200.9029   $200.90   $200.90   $200.90  
  Purchase #2 $206.92   3.422%   $214.0008   $214.00   $214.00   $214.00  
  Purchase #3 $120.30   4.689%   $125.9409   $125.94   $125.95   $125.90  
  Purchase #4 $90.65   3.762%   $94.0603   $94.06   $94.05   $94.10  
  Purchase #5 $200.90   3.362%   $207.6543   $207.65   $207.65   $207.70  
  Purchase #6 $249.86   5.839%   $264.4493   $264.45   $264.45   $264.40  
  Purchase #7 $73.45   3.609%   $76.1008   $76.10   $76.10   $76.10  
  7 purchase totals = $1,135.94       $1,183.1093   $1,183.10   $1,183.10   $1,183.10