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 $24.92   5.387%   $26.2624   $26.26   $26.25   $26.30  
  Purchase #2 $230.50   5.555%   $243.3043   $243.30   $243.30   $243.30  
  Purchase #3 $99.26   10.162%   $109.3468   $109.35   $109.35   $109.30  
  Purchase #4 $81.52   5.369%   $85.8968   $85.90   $85.90   $85.90  
  Purchase #5 $246.27   3.811%   $255.6553   $255.66   $255.65   $255.70  
  Purchase #6 $115.78   3.846%   $120.2329   $120.23   $120.25   $120.20  
  Purchase #7 $30.74   12.272%   $34.5124   $34.51   $34.50   $34.50  
  7 purchase totals = $828.99       $875.2109   $875.21   $875.20   $875.20