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 $176.58   8.586%   $191.7412   $191.74   $191.75   $191.70  
  Purchase #2 $19.59   11.196%   $21.7833   $21.78   $21.80   $21.80  
  Purchase #3 $199.90   3.529%   $206.9545   $206.95   $206.95   $207.00  
  Purchase #4 $134.65   8.479%   $146.067   $146.07   $146.05   $146.10  
  Purchase #5 $120.80   5.867%   $127.8873   $127.89   $127.90   $127.90  
  Purchase #6 $184.96   4.262%   $192.843   $192.84   $192.85   $192.80  
  Purchase #7 $206.57   5.156%   $217.2207   $217.22   $217.20   $217.20  
  7 purchase totals = $1,043.05       $1,104.4970   $1,104.49   $1,104.50   $1,104.50