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 $215.43   5.380%   $227.0201   $227.02   $227.00   $227.00  
  Purchase #2 $208.57   13.794%   $237.3401   $237.34   $237.35   $237.30  
  Purchase #3 $208.97   10.311%   $230.5169   $230.52   $230.50   $230.50  
  Purchase #4 $136.53   4.409%   $142.5496   $142.55   $142.55   $142.50  
  Purchase #5 $203.82   13.103%   $230.5265   $230.53   $230.55   $230.50  
  Purchase #6 $26.43   8.449%   $28.6631   $28.66   $28.65   $28.70  
  Purchase #7 $152.78   12.427%   $171.766   $171.77   $171.75   $171.80  
  7 purchase totals = $1,152.53       $1,268.3823   $1,268.39   $1,268.35   $1,268.30