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 $34.73   3.720%   $36.022   $36.02   $36.00   $36.00  
  Purchase #2 $144.97   9.286%   $158.4319   $158.43   $158.45   $158.40  
  Purchase #3 $184.54   13.229%   $208.9528   $208.95   $208.95   $209.00  
  Purchase #4 $212.40   11.277%   $236.3523   $236.35   $236.35   $236.40  
  Purchase #5 $244.58   12.694%   $275.627   $275.63   $275.65   $275.60  
  Purchase #6 $63.69   10.451%   $70.3462   $70.35   $70.35   $70.30  
  Purchase #7 $148.52   11.121%   $165.0369   $165.04   $165.05   $165.00  
  7 purchase totals = $1,033.43       $1,150.7691   $1,150.77   $1,150.80   $1,150.70