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 $90.84   4.359%   $94.7997   $94.80   $94.80   $94.80  
  Purchase #2 $173.55   10.774%   $192.2483   $192.25   $192.25   $192.20  
  Purchase #3 $158.88   11.788%   $177.6088   $177.61   $177.60   $177.60  
  Purchase #4 $159.27   7.668%   $171.4828   $171.48   $171.50   $171.50  
  Purchase #5 $89.79   7.153%   $96.2127   $96.21   $96.20   $96.20  
  Purchase #6 $6.91   13.770%   $7.8615   $7.86   $7.85   $7.90  
  Purchase #7 $18.91   10.181%   $20.8352   $20.84   $20.85   $20.80  
  7 purchase totals = $698.15       $761.0490   $761.05   $761.05   $761.00