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 $207.28   13.288%   $234.8234   $234.82   $234.80   $234.80  
  Purchase #2 $31.68   13.856%   $36.0696   $36.07   $36.05   $36.10  
  Purchase #3 $206.86   10.409%   $228.3921   $228.39   $228.40   $228.40  
  Purchase #4 $40.77   8.686%   $44.3113   $44.31   $44.30   $44.30  
  Purchase #5 $171.66   13.749%   $195.2615   $195.26   $195.25   $195.30  
  Purchase #6 $204.31   3.314%   $211.0808   $211.08   $211.10   $211.10  
  Purchase #7 $70.55   3.423%   $72.9649   $72.96   $72.95   $73.00  
  7 purchase totals = $933.11       $1,022.9036   $1,022.89   $1,022.85   $1,023.00