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 $162.29   13.600%   $184.3614   $184.36   $184.35   $184.40  
  Purchase #2 $55.25   9.787%   $60.6573   $60.66   $60.65   $60.70  
  Purchase #3 $161.49   10.451%   $178.3673   $178.37   $178.35   $178.40  
  Purchase #4 $191.97   4.354%   $200.3284   $200.33   $200.35   $200.30  
  Purchase #5 $161.31   6.572%   $171.9113   $171.91   $171.90   $171.90  
  Purchase #6 $169.90   8.856%   $184.9463   $184.95   $184.95   $184.90  
  Purchase #7 $102.91   11.865%   $115.1203   $115.12   $115.10   $115.10  
  7 purchase totals = $1,005.12       $1,095.6923   $1,095.70   $1,095.65   $1,095.70