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 $189.54   11.664%   $211.6479   $211.65   $211.65   $211.60  
  Purchase #2 $198.61   6.465%   $211.4501   $211.45   $211.45   $211.50  
  Purchase #3 $60.45   4.297%   $63.0475   $63.05   $63.05   $63.00  
  Purchase #4 $77.26   11.742%   $86.3319   $86.33   $86.35   $86.30  
  Purchase #5 $83.87   4.307%   $87.4823   $87.48   $87.50   $87.50  
  Purchase #6 $87.77   8.356%   $95.1041   $95.10   $95.10   $95.10  
  Purchase #7 $41.95   10.447%   $46.3325   $46.33   $46.35   $46.30  
  7 purchase totals = $739.45       $801.3963   $801.39   $801.45   $801.30