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 $84.29   13.514%   $95.681   $95.68   $95.70   $95.70  
  Purchase #2 $120.79   11.166%   $134.2774   $134.28   $134.30   $134.30  
  Purchase #3 $110.86   13.251%   $125.5501   $125.55   $125.55   $125.60  
  Purchase #4 $126.61   4.826%   $132.7202   $132.72   $132.70   $132.70  
  Purchase #5 $19.60   7.597%   $21.089   $21.09   $21.10   $21.10  
  Purchase #6 $206.62   12.775%   $233.0157   $233.02   $233.00   $233.00  
  Purchase #7 $161.42   12.164%   $181.0551   $181.06   $181.05   $181.10  
  7 purchase totals = $830.19       $923.3885   $923.40   $923.40   $923.50