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 $65.68   7.539%   $70.6316   $70.63   $70.65   $70.60  
  Purchase #2 $152.52   8.866%   $166.0424   $166.04   $166.05   $166.00  
  Purchase #3 $199.33   7.745%   $214.7681   $214.77   $214.75   $214.80  
  Purchase #4 $197.62   7.695%   $212.8269   $212.83   $212.85   $212.80  
  Purchase #5 $8.62   5.255%   $9.073   $9.07   $9.05   $9.10  
  Purchase #6 $18.94   6.512%   $20.1734   $20.17   $20.15   $20.20  
  Purchase #7 $235.61   9.600%   $258.2286   $258.23   $258.25   $258.20  
  7 purchase totals = $878.32       $951.7440   $951.74   $951.75   $951.70