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 $186.60   3.257%   $192.6776   $192.68   $192.70   $192.70  
  Purchase #2 $211.88   11.161%   $235.5279   $235.53   $235.55   $235.50  
  Purchase #3 $115.36   9.456%   $126.2684   $126.27   $126.25   $126.30  
  Purchase #4 $245.98   9.137%   $268.4552   $268.46   $268.45   $268.50  
  Purchase #5 $176.75   11.142%   $196.4435   $196.44   $196.45   $196.40  
  Purchase #6 $181.48   11.645%   $202.6133   $202.61   $202.60   $202.60  
  Purchase #7 $130.50   6.297%   $138.7176   $138.72   $138.70   $138.70  
  7 purchase totals = $1,248.55       $1,360.7035   $1,360.71   $1,360.70   $1,360.70