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 $153.41   5.142%   $161.2983   $161.30   $161.30   $161.30  
  Purchase #2 $238.80   5.648%   $252.2874   $252.29   $252.30   $252.30  
  Purchase #3 $77.49   11.761%   $86.6036   $86.60   $86.60   $86.60  
  Purchase #4 $208.83   5.196%   $219.6808   $219.68   $219.70   $219.70  
  Purchase #5 $112.52   10.870%   $124.7509   $124.75   $124.75   $124.80  
  Purchase #6 $218.96   13.361%   $248.2152   $248.22   $248.20   $248.20  
  Purchase #7 $244.71   6.523%   $260.6724   $260.67   $260.65   $260.70  
  7 purchase totals = $1,254.72       $1,353.5086   $1,353.51   $1,353.50   $1,353.60