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 $217.29   8.616%   $236.0117   $236.01   $236.00   $236.00  
  Purchase #2 $214.84   13.237%   $243.2784   $243.28   $243.30   $243.30  
  Purchase #3 $220.66   6.737%   $235.5259   $235.53   $235.55   $235.50  
  Purchase #4 $174.50   9.464%   $191.0147   $191.01   $191.00   $191.00  
  Purchase #5 $210.92   3.229%   $217.7306   $217.73   $217.75   $217.70  
  Purchase #6 $13.87   12.753%   $15.6388   $15.64   $15.65   $15.60  
  Purchase #7 $13.59   6.273%   $14.4425   $14.44   $14.45   $14.40  
  7 purchase totals = $1,065.67       $1,153.6426   $1,153.64   $1,153.70   $1,153.50