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 $86.52   12.791%   $97.5868   $97.59   $97.60   $97.60  
  Purchase #2 $91.40   11.311%   $101.7383   $101.74   $101.75   $101.70  
  Purchase #3 $52.94   6.841%   $56.5616   $56.56   $56.55   $56.60  
  Purchase #4 $240.99   6.756%   $257.2713   $257.27   $257.25   $257.30  
  Purchase #5 $244.71   6.560%   $260.763   $260.76   $260.75   $260.80  
  Purchase #6 $68.70   12.265%   $77.1261   $77.13   $77.15   $77.10  
  Purchase #7 $246.75   4.116%   $256.9062   $256.91   $256.90   $256.90  
  7 purchase totals = $1,032.01       $1,107.9533   $1,107.96   $1,107.95   $1,108.00