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 $167.52   5.809%   $177.2512   $177.25   $177.25   $177.30  
  Purchase #2 $22.37   11.446%   $24.9305   $24.93   $24.95   $24.90  
  Purchase #3 $8.86   7.582%   $9.5318   $9.53   $9.55   $9.50  
  Purchase #4 $127.85   4.533%   $133.6454   $133.65   $133.65   $133.60  
  Purchase #5 $182.26   10.231%   $200.907   $200.91   $200.90   $200.90  
  Purchase #6 $154.63   11.737%   $172.7789   $172.78   $172.80   $172.80  
  Purchase #7 $69.74   4.815%   $73.098   $73.10   $73.10   $73.10  
  7 purchase totals = $733.23       $792.1428   $792.15   $792.20   $792.10