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 $62.61   11.207%   $69.6267   $69.63   $69.65   $69.60  
  Purchase #2 $169.84   13.342%   $192.5001   $192.50   $192.50   $192.50  
  Purchase #3 $117.69   11.799%   $131.5762   $131.58   $131.60   $131.60  
  Purchase #4 $67.92   3.679%   $70.4188   $70.42   $70.40   $70.40  
  Purchase #5 $192.98   5.746%   $204.0686   $204.07   $204.05   $204.10  
  Purchase #6 $73.33   3.661%   $76.0146   $76.01   $76.00   $76.00  
  Purchase #7 $63.52   11.199%   $70.6336   $70.63   $70.65   $70.60  
  7 purchase totals = $747.89       $814.8386   $814.84   $814.85   $814.80