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 $88.75   8.303%   $96.1189   $96.12   $96.10   $96.10  
  Purchase #2 $195.53   10.417%   $215.8984   $215.90   $215.90   $215.90  
  Purchase #3 $231.34   13.709%   $263.0544   $263.05   $263.05   $263.10  
  Purchase #4 $56.66   10.470%   $62.5923   $62.59   $62.60   $62.60  
  Purchase #5 $71.95   7.738%   $77.5175   $77.52   $77.50   $77.50  
  Purchase #6 $171.55   5.408%   $180.8274   $180.83   $180.85   $180.80  
  Purchase #7 $31.84   5.589%   $33.6195   $33.62   $33.60   $33.60  
  7 purchase totals = $847.62       $929.6284   $929.63   $929.60   $929.60