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 $204.84   5.773%   $216.6654   $216.67   $216.65   $216.70  
  Purchase #2 $187.78   6.293%   $199.597   $199.60   $199.60   $199.60  
  Purchase #3 $95.96   7.186%   $102.8557   $102.86   $102.85   $102.90  
  Purchase #4 $68.92   6.681%   $73.5245   $73.52   $73.50   $73.50  
  Purchase #5 $192.59   3.683%   $199.6831   $199.68   $199.70   $199.70  
  Purchase #6 $71.43   3.562%   $73.9743   $73.97   $73.95   $74.00  
  Purchase #7 $198.51   4.343%   $207.1313   $207.13   $207.15   $207.10  
  7 purchase totals = $1,020.03       $1,073.4313   $1,073.43   $1,073.40   $1,073.50