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 $183.74   9.394%   $201.0005   $201.00   $201.00   $201.00  
  Purchase #2 $170.42   10.576%   $188.4436   $188.44   $188.45   $188.40  
  Purchase #3 $193.91   6.174%   $205.882   $205.88   $205.90   $205.90  
  Purchase #4 $127.84   6.644%   $136.3337   $136.33   $136.35   $136.30  
  Purchase #5 $160.85   6.690%   $171.6109   $171.61   $171.60   $171.60  
  Purchase #6 $30.65   11.312%   $34.1171   $34.12   $34.10   $34.10  
  Purchase #7 $139.65   13.196%   $158.0782   $158.08   $158.10   $158.10  
  7 purchase totals = $1,007.06       $1,095.4660   $1,095.46   $1,095.50   $1,095.40