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 $104.37   9.543%   $114.33   $114.33   $114.35   $114.30  
  Purchase #2 $175.99   8.857%   $191.5774   $191.58   $191.60   $191.60  
  Purchase #3 $115.34   12.570%   $129.8382   $129.84   $129.85   $129.80  
  Purchase #4 $174.64   3.601%   $180.9288   $180.93   $180.95   $180.90  
  Purchase #5 $219.36   8.179%   $237.3015   $237.30   $237.30   $237.30  
  Purchase #6 $38.92   4.281%   $40.5862   $40.59   $40.60   $40.60  
  Purchase #7 $113.94   3.143%   $117.5211   $117.52   $117.50   $117.50  
  7 purchase totals = $942.56       $1,012.0832   $1,012.09   $1,012.15   $1,012.00