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 $62.78   6.810%   $67.0553   $67.06   $67.05   $67.10  
  Purchase #2 $87.52   3.550%   $90.627   $90.63   $90.65   $90.60  
  Purchase #3 $174.85   9.844%   $192.0622   $192.06   $192.05   $192.10  
  Purchase #4 $203.62   8.181%   $220.2782   $220.28   $220.30   $220.30  
  Purchase #5 $44.28   9.517%   $48.4941   $48.49   $48.50   $48.50  
  Purchase #6 $48.43   3.682%   $50.2132   $50.21   $50.20   $50.20  
  Purchase #7 $80.62   8.143%   $87.1849   $87.18   $87.20   $87.20  
  7 purchase totals = $702.10       $755.9149   $755.91   $755.95   $756.00