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 $194.77   3.562%   $201.7077   $201.71   $201.70   $201.70  
  Purchase #2 $114.57   7.154%   $122.7663   $122.77   $122.75   $122.80  
  Purchase #3 $185.57   4.735%   $194.3567   $194.36   $194.35   $194.40  
  Purchase #4 $163.50   9.367%   $178.815   $178.82   $178.80   $178.80  
  Purchase #5 $134.62   9.350%   $147.207   $147.21   $147.20   $147.20  
  Purchase #6 $44.33   6.657%   $47.281   $47.28   $47.30   $47.30  
  Purchase #7 $155.57   7.319%   $166.9562   $166.96   $166.95   $167.00  
  7 purchase totals = $992.93       $1,059.0899   $1,059.11   $1,059.05   $1,059.20