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 $46.30   13.659%   $52.6241   $52.62   $52.60   $52.60  
  Purchase #2 $245.38   8.263%   $265.6557   $265.66   $265.65   $265.70  
  Purchase #3 $64.97   7.354%   $69.7479   $69.75   $69.75   $69.70  
  Purchase #4 $181.35   5.727%   $191.7359   $191.74   $191.75   $191.70  
  Purchase #5 $238.92   13.179%   $270.4073   $270.41   $270.40   $270.40  
  Purchase #6 $135.99   11.608%   $151.7757   $151.78   $151.80   $151.80  
  Purchase #7 $130.33   12.800%   $147.0122   $147.01   $147.00   $147.00  
  7 purchase totals = $1,043.24       $1,148.9588   $1,148.97   $1,148.95   $1,148.90