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 $193.36   5.377%   $203.757   $203.76   $203.75   $203.80  
  Purchase #2 $243.40   8.276%   $263.5438   $263.54   $263.55   $263.50  
  Purchase #3 $157.84   6.600%   $168.2574   $168.26   $168.25   $168.30  
  Purchase #4 $202.26   13.843%   $230.2589   $230.26   $230.25   $230.30  
  Purchase #5 $141.57   13.862%   $161.1944   $161.19   $161.20   $161.20  
  Purchase #6 $23.57   13.790%   $26.8203   $26.82   $26.80   $26.80  
  Purchase #7 $87.82   11.686%   $98.0826   $98.08   $98.10   $98.10  
  7 purchase totals = $1,049.82       $1,151.9144   $1,151.91   $1,151.90   $1,152.00