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 $33.42   7.352%   $35.877   $35.88   $35.90   $35.90  
  Purchase #2 $170.89   9.247%   $186.6922   $186.69   $186.70   $186.70  
  Purchase #3 $194.58   5.475%   $205.2333   $205.23   $205.25   $205.20  
  Purchase #4 $159.26   11.634%   $177.7883   $177.79   $177.80   $177.80  
  Purchase #5 $116.61   6.167%   $123.8013   $123.80   $123.80   $123.80  
  Purchase #6 $169.35   9.480%   $185.4044   $185.40   $185.40   $185.40  
  Purchase #7 $116.77   3.230%   $120.5417   $120.54   $120.55   $120.50  
  7 purchase totals = $960.88       $1,035.3382   $1,035.33   $1,035.40   $1,035.30