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 $68.29   11.337%   $76.032   $76.03   $76.05   $76.00  
  Purchase #2 $89.62   10.273%   $98.8267   $98.83   $98.85   $98.80  
  Purchase #3 $206.34   12.816%   $232.7845   $232.78   $232.80   $232.80  
  Purchase #4 $74.97   10.162%   $82.5885   $82.59   $82.60   $82.60  
  Purchase #5 $148.30   5.603%   $156.6092   $156.61   $156.60   $156.60  
  Purchase #6 $34.52   10.445%   $38.1256   $38.13   $38.15   $38.10  
  Purchase #7 $100.61   9.507%   $110.175   $110.18   $110.20   $110.20  
  7 purchase totals = $722.65       $795.1415   $795.15   $795.25   $795.10