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 $247.77   5.866%   $262.3042   $262.30   $262.30   $262.30  
  Purchase #2 $79.91   7.470%   $85.8793   $85.88   $85.90   $85.90  
  Purchase #3 $166.90   8.242%   $180.6559   $180.66   $180.65   $180.70  
  Purchase #4 $211.96   12.811%   $239.1142   $239.11   $239.10   $239.10  
  Purchase #5 $159.69   6.221%   $169.6243   $169.62   $169.60   $169.60  
  Purchase #6 $109.36   12.145%   $122.6418   $122.64   $122.65   $122.60  
  Purchase #7 $85.80   6.229%   $91.1445   $91.14   $91.15   $91.10  
  7 purchase totals = $1,061.39       $1,151.3642   $1,151.35   $1,151.35   $1,151.30