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 $44.98   3.583%   $46.5916   $46.59   $46.60   $46.60  
  Purchase #2 $133.31   13.784%   $151.6855   $151.69   $151.70   $151.70  
  Purchase #3 $38.25   11.833%   $42.7761   $42.78   $42.80   $42.80  
  Purchase #4 $163.45   13.317%   $185.2166   $185.22   $185.20   $185.20  
  Purchase #5 $38.70   8.745%   $42.0843   $42.08   $42.10   $42.10  
  Purchase #6 $239.88   4.721%   $251.2047   $251.20   $251.20   $251.20  
  Purchase #7 $204.84   10.545%   $226.4404   $226.44   $226.45   $226.40  
  7 purchase totals = $863.41       $945.9992   $946.00   $946.05   $946.00