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 $86.26   9.641%   $94.5763   $94.58   $94.60   $94.60  
  Purchase #2 $111.72   5.358%   $117.706   $117.71   $117.70   $117.70  
  Purchase #3 $58.45   11.211%   $65.0028   $65.00   $65.00   $65.00  
  Purchase #4 $44.59   6.651%   $47.5557   $47.56   $47.55   $47.60  
  Purchase #5 $244.85   12.263%   $274.876   $274.88   $274.90   $274.90  
  Purchase #6 $27.84   7.436%   $29.9102   $29.91   $29.90   $29.90  
  Purchase #7 $147.91   10.449%   $163.3651   $163.37   $163.35   $163.40  
  7 purchase totals = $721.62       $792.9921   $793.01   $793.00   $793.10