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 $88.58   6.102%   $93.9852   $93.99   $94.00   $94.00  
  Purchase #2 $221.80   10.775%   $245.699   $245.70   $245.70   $245.70  
  Purchase #3 $246.29   7.743%   $265.3602   $265.36   $265.35   $265.40  
  Purchase #4 $159.79   10.490%   $176.552   $176.55   $176.55   $176.60  
  Purchase #5 $145.39   9.788%   $159.6208   $159.62   $159.60   $159.60  
  Purchase #6 $40.98   13.647%   $46.5725   $46.57   $46.55   $46.60  
  Purchase #7 $195.51   6.558%   $208.3315   $208.33   $208.35   $208.30  
  7 purchase totals = $1,098.34       $1,196.1212   $1,196.12   $1,196.10   $1,196.20