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 $152.69   5.803%   $161.5506   $161.55   $161.55   $161.60  
  Purchase #2 $178.26   13.706%   $202.6923   $202.69   $202.70   $202.70  
  Purchase #3 $244.84   3.203%   $252.6822   $252.68   $252.70   $252.70  
  Purchase #4 $110.52   6.857%   $118.0984   $118.10   $118.10   $118.10  
  Purchase #5 $234.90   5.111%   $246.9057   $246.91   $246.90   $246.90  
  Purchase #6 $239.41   9.702%   $262.6376   $262.64   $262.65   $262.60  
  Purchase #7 $158.94   6.374%   $169.0708   $169.07   $169.05   $169.10  
  7 purchase totals = $1,319.56       $1,413.6376   $1,413.64   $1,413.65   $1,413.70