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 $224.42   5.163%   $236.0068   $236.01   $236.00   $236.00  
  Purchase #2 $220.39   7.259%   $236.3881   $236.39   $236.40   $236.40  
  Purchase #3 $29.83   5.811%   $31.5634   $31.56   $31.55   $31.60  
  Purchase #4 $146.72   4.415%   $153.1977   $153.20   $153.20   $153.20  
  Purchase #5 $206.50   13.540%   $234.4601   $234.46   $234.45   $234.50  
  Purchase #6 $215.66   6.145%   $228.9123   $228.91   $228.90   $228.90  
  Purchase #7 $50.87   3.850%   $52.8285   $52.83   $52.85   $52.80  
  7 purchase totals = $1,094.39       $1,173.3569   $1,173.36   $1,173.35   $1,173.40