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 $87.61   10.331%   $96.661   $96.66   $96.65   $96.70  
  Purchase #2 $220.86   9.267%   $241.3271   $241.33   $241.35   $241.30  
  Purchase #3 $157.80   11.837%   $176.4788   $176.48   $176.50   $176.50  
  Purchase #4 $97.66   11.509%   $108.8997   $108.90   $108.90   $108.90  
  Purchase #5 $205.41   11.641%   $229.3218   $229.32   $229.30   $229.30  
  Purchase #6 $236.92   4.169%   $246.7972   $246.80   $246.80   $246.80  
  Purchase #7 $170.91   9.322%   $186.8422   $186.84   $186.85   $186.80  
  7 purchase totals = $1,177.17       $1,286.3278   $1,286.33   $1,286.35   $1,286.30