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 $204.68   4.551%   $213.995   $214.00   $214.00   $214.00  
  Purchase #2 $51.52   6.308%   $54.7699   $54.77   $54.75   $54.80  
  Purchase #3 $51.82   3.359%   $53.5606   $53.56   $53.55   $53.60  
  Purchase #4 $225.71   3.116%   $232.7431   $232.74   $232.75   $232.70  
  Purchase #5 $179.33   4.554%   $187.4967   $187.50   $187.50   $187.50  
  Purchase #6 $209.41   13.857%   $238.4279   $238.43   $238.45   $238.40  
  Purchase #7 $189.71   6.497%   $202.0355   $202.04   $202.05   $202.00  
  7 purchase totals = $1,112.18       $1,183.0287   $1,183.04   $1,183.05   $1,183.00