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 $145.74   5.504%   $153.7615   $153.76   $153.75   $153.80  
  Purchase #2 $202.69   10.674%   $224.3251   $224.33   $224.35   $224.30  
  Purchase #3 $214.74   11.586%   $239.6198   $239.62   $239.60   $239.60  
  Purchase #4 $12.43   13.539%   $14.1129   $14.11   $14.10   $14.10  
  Purchase #5 $38.71   13.554%   $43.9568   $43.96   $43.95   $44.00  
  Purchase #6 $203.27   7.555%   $218.627   $218.63   $218.65   $218.60  
  Purchase #7 $122.52   6.867%   $130.9334   $130.93   $130.95   $130.90  
  7 purchase totals = $940.10       $1,025.3365   $1,025.34   $1,025.35   $1,025.30