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 $58.79   6.710%   $62.7348   $62.73   $62.75   $62.70  
  Purchase #2 $221.65   9.543%   $242.8021   $242.80   $242.80   $242.80  
  Purchase #3 $247.37   9.368%   $270.5436   $270.54   $270.55   $270.50  
  Purchase #4 $105.42   5.244%   $110.9482   $110.95   $110.95   $110.90  
  Purchase #5 $32.86   7.469%   $35.3143   $35.31   $35.30   $35.30  
  Purchase #6 $169.44   7.233%   $181.6956   $181.70   $181.70   $181.70  
  Purchase #7 $196.71   3.304%   $203.2093   $203.21   $203.20   $203.20  
  7 purchase totals = $1,032.24       $1,107.2479   $1,107.24   $1,107.25   $1,107.10