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 $67.54   5.393%   $71.1824   $71.18   $71.20   $71.20  
  Purchase #2 $39.69   4.366%   $41.4229   $41.42   $41.40   $41.40  
  Purchase #3 $163.82   5.458%   $172.7613   $172.76   $172.75   $172.80  
  Purchase #4 $203.43   11.142%   $226.0962   $226.10   $226.10   $226.10  
  Purchase #5 $168.43   8.721%   $183.1188   $183.12   $183.10   $183.10  
  Purchase #6 $59.53   11.282%   $66.2462   $66.25   $66.25   $66.20  
  Purchase #7 $182.74   10.608%   $202.1251   $202.13   $202.15   $202.10  
  7 purchase totals = $885.18       $962.9529   $962.96   $962.95   $962.90