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 $93.28   3.573%   $96.6129   $96.61   $96.60   $96.60  
  Purchase #2 $101.84   13.753%   $115.8461   $115.85   $115.85   $115.80  
  Purchase #3 $16.34   4.377%   $17.0552   $17.06   $17.05   $17.10  
  Purchase #4 $223.46   4.849%   $234.2956   $234.30   $234.30   $234.30  
  Purchase #5 $156.64   3.262%   $161.7496   $161.75   $161.75   $161.70  
  Purchase #6 $232.39   5.474%   $245.111   $245.11   $245.10   $245.10  
  Purchase #7 $195.78   5.565%   $206.6752   $206.68   $206.70   $206.70  
  7 purchase totals = $1,019.73       $1,077.3456   $1,077.36   $1,077.35   $1,077.30