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 $56.42   4.385%   $58.894   $58.89   $58.90   $58.90  
  Purchase #2 $59.72   4.391%   $62.3423   $62.34   $62.35   $62.30  
  Purchase #3 $157.94   13.124%   $178.668   $178.67   $178.65   $178.70  
  Purchase #4 $226.40   9.824%   $248.6415   $248.64   $248.65   $248.60  
  Purchase #5 $111.26   3.525%   $115.1819   $115.18   $115.20   $115.20  
  Purchase #6 $230.36   9.135%   $251.4034   $251.40   $251.40   $251.40  
  Purchase #7 $167.48   7.677%   $180.3374   $180.34   $180.35   $180.30  
  7 purchase totals = $1,009.58       $1,095.4685   $1,095.46   $1,095.50   $1,095.40