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 $44.37   8.597%   $48.1845   $48.18   $48.20   $48.20  
  Purchase #2 $145.36   9.149%   $158.659   $158.66   $158.65   $158.70  
  Purchase #3 $216.37   6.509%   $230.4535   $230.45   $230.45   $230.50  
  Purchase #4 $230.40   11.567%   $257.0504   $257.05   $257.05   $257.10  
  Purchase #5 $24.75   4.678%   $25.9078   $25.91   $25.90   $25.90  
  Purchase #6 $75.88   8.584%   $82.3935   $82.39   $82.40   $82.40  
  Purchase #7 $243.98   5.494%   $257.3843   $257.38   $257.40   $257.40  
  7 purchase totals = $981.11       $1,060.0330   $1,060.02   $1,060.05   $1,060.20