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 $176.82   13.799%   $201.2194   $201.22   $201.20   $201.20  
  Purchase #2 $143.72   5.694%   $151.9034   $151.90   $151.90   $151.90  
  Purchase #3 $145.30   4.761%   $152.2177   $152.22   $152.20   $152.20  
  Purchase #4 $224.99   4.179%   $234.3923   $234.39   $234.40   $234.40  
  Purchase #5 $55.91   13.393%   $63.398   $63.40   $63.40   $63.40  
  Purchase #6 $167.64   5.297%   $176.5199   $176.52   $176.50   $176.50  
  Purchase #7 $121.77   8.394%   $131.9914   $131.99   $132.00   $132.00  
  7 purchase totals = $1,036.15       $1,111.6421   $1,111.64   $1,111.60   $1,111.60