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 $97.82   4.806%   $102.5212   $102.52   $102.50   $102.50  
  Purchase #2 $214.26   10.755%   $237.3037   $237.30   $237.30   $237.30  
  Purchase #3 $86.41   12.373%   $97.1015   $97.10   $97.10   $97.10  
  Purchase #4 $225.31   4.286%   $234.9668   $234.97   $234.95   $235.00  
  Purchase #5 $42.85   6.106%   $45.4664   $45.47   $45.45   $45.50  
  Purchase #6 $220.78   6.787%   $235.7643   $235.76   $235.75   $235.80  
  Purchase #7 $58.74   4.761%   $61.5366   $61.54   $61.55   $61.50  
  7 purchase totals = $946.17       $1,014.6605   $1,014.66   $1,014.60   $1,014.70