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 $86.67   12.713%   $97.6884   $97.69   $97.70   $97.70  
  Purchase #2 $202.37   4.624%   $211.7276   $211.73   $211.75   $211.70  
  Purchase #3 $240.65   9.129%   $262.6189   $262.62   $262.60   $262.60  
  Purchase #4 $173.60   12.717%   $195.6767   $195.68   $195.70   $195.70  
  Purchase #5 $38.27   6.396%   $40.7177   $40.72   $40.70   $40.70  
  Purchase #6 $180.96   6.330%   $192.4148   $192.41   $192.40   $192.40  
  Purchase #7 $129.88   13.507%   $147.4229   $147.42   $147.40   $147.40  
  7 purchase totals = $1,052.40       $1,148.2670   $1,148.27   $1,148.25   $1,148.20