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 $214.28   9.230%   $234.058   $234.06   $234.05   $234.10  
  Purchase #2 $44.51   6.770%   $47.5233   $47.52   $47.50   $47.50  
  Purchase #3 $89.93   4.595%   $94.0623   $94.06   $94.05   $94.10  
  Purchase #4 $209.60   12.572%   $235.9509   $235.95   $235.95   $236.00  
  Purchase #5 $139.63   5.565%   $147.4004   $147.40   $147.40   $147.40  
  Purchase #6 $219.29   3.622%   $227.2327   $227.23   $227.25   $227.20  
  Purchase #7 $169.62   11.647%   $189.3756   $189.38   $189.40   $189.40  
  7 purchase totals = $1,086.86       $1,175.6032   $1,175.60   $1,175.60   $1,175.70