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 $84.46   12.532%   $95.0445   $95.04   $95.05   $95.00  
  Purchase #2 $8.85   13.207%   $10.0188   $10.02   $10.00   $10.00  
  Purchase #3 $206.85   13.239%   $234.2349   $234.23   $234.25   $234.20  
  Purchase #4 $109.45   5.543%   $115.5168   $115.52   $115.50   $115.50  
  Purchase #5 $189.40   12.146%   $212.4045   $212.40   $212.40   $212.40  
  Purchase #6 $100.69   6.161%   $106.8935   $106.89   $106.90   $106.90  
  Purchase #7 $169.95   13.604%   $193.07   $193.07   $193.05   $193.10  
  7 purchase totals = $869.65       $967.1830   $967.17   $967.15   $967.10