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 $216.53   8.524%   $234.987   $234.99   $235.00   $235.00  
  Purchase #2 $242.52   9.134%   $264.6718   $264.67   $264.65   $264.70  
  Purchase #3 $152.33   13.646%   $173.117   $173.12   $173.10   $173.10  
  Purchase #4 $185.27   4.638%   $193.8628   $193.86   $193.85   $193.90  
  Purchase #5 $84.96   4.456%   $88.7458   $88.75   $88.75   $88.70  
  Purchase #6 $103.28   5.283%   $108.7363   $108.74   $108.75   $108.70  
  Purchase #7 $190.26   9.153%   $207.6745   $207.67   $207.65   $207.70  
  7 purchase totals = $1,175.15       $1,271.7952   $1,271.80   $1,271.75   $1,271.80