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 $216.92   13.242%   $245.6445   $245.64   $245.65   $245.60  
  Purchase #2 $225.26   10.390%   $248.6645   $248.66   $248.65   $248.70  
  Purchase #3 $230.38   9.312%   $251.833   $251.83   $251.85   $251.80  
  Purchase #4 $68.94   8.210%   $74.6   $74.60   $74.60   $74.60  
  Purchase #5 $226.82   7.420%   $243.65   $243.65   $243.65   $243.70  
  Purchase #6 $238.29   4.114%   $248.0933   $248.09   $248.10   $248.10  
  Purchase #7 $151.42   7.681%   $163.0506   $163.05   $163.05   $163.10  
  7 purchase totals = $1,358.03       $1,475.5359   $1,475.52   $1,475.55   $1,475.60