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 $60.39   13.766%   $68.7033   $68.70   $68.70   $68.70  
  Purchase #2 $222.49   9.802%   $244.2985   $244.30   $244.30   $244.30  
  Purchase #3 $153.88   7.238%   $165.0178   $165.02   $165.00   $165.00  
  Purchase #4 $238.38   4.246%   $248.5016   $248.50   $248.50   $248.50  
  Purchase #5 $70.48   12.793%   $79.4965   $79.50   $79.50   $79.50  
  Purchase #6 $216.57   8.363%   $234.6817   $234.68   $234.70   $234.70  
  Purchase #7 $173.45   7.623%   $186.6721   $186.67   $186.65   $186.70  
  7 purchase totals = $1,135.64       $1,227.3715   $1,227.37   $1,227.35   $1,227.40