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 $239.48   11.629%   $267.3291   $267.33   $267.35   $267.30  
  Purchase #2 $217.38   8.359%   $235.5508   $235.55   $235.55   $235.60  
  Purchase #3 $169.52   7.127%   $181.6017   $181.60   $181.60   $181.60  
  Purchase #4 $65.51   9.831%   $71.9503   $71.95   $71.95   $72.00  
  Purchase #5 $206.29   4.340%   $215.243   $215.24   $215.25   $215.20  
  Purchase #6 $69.84   4.324%   $72.8599   $72.86   $72.85   $72.90  
  Purchase #7 $106.55   9.522%   $116.6957   $116.70   $116.70   $116.70  
  7 purchase totals = $1,074.57       $1,161.2305   $1,161.23   $1,161.25   $1,161.30