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 $84.29   12.688%   $94.9847   $94.98   $95.00   $95.00  
  Purchase #2 $121.83   4.123%   $126.8531   $126.85   $126.85   $126.90  
  Purchase #3 $200.51   11.466%   $223.5005   $223.50   $223.50   $223.50  
  Purchase #4 $131.64   8.644%   $143.019   $143.02   $143.00   $143.00  
  Purchase #5 $152.26   8.429%   $165.094   $165.09   $165.10   $165.10  
  Purchase #6 $32.66   10.461%   $36.0766   $36.08   $36.10   $36.10  
  Purchase #7 $236.40   13.287%   $267.8105   $267.81   $267.80   $267.80  
  7 purchase totals = $959.59       $1,057.3384   $1,057.33   $1,057.35   $1,057.40