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 $68.32   12.628%   $76.9474   $76.95   $76.95   $76.90  
  Purchase #2 $218.50   4.791%   $228.9683   $228.97   $228.95   $229.00  
  Purchase #3 $244.46   7.684%   $263.2443   $263.24   $263.25   $263.20  
  Purchase #4 $129.36   11.462%   $144.1872   $144.19   $144.20   $144.20  
  Purchase #5 $63.28   9.301%   $69.1657   $69.17   $69.15   $69.20  
  Purchase #6 $90.52   12.147%   $101.5155   $101.52   $101.50   $101.50  
  Purchase #7 $191.47   6.814%   $204.5168   $204.52   $204.50   $204.50  
  7 purchase totals = $1,005.91       $1,088.5452   $1,088.56   $1,088.50   $1,088.50