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 $244.26   10.273%   $269.3528   $269.35   $269.35   $269.40  
  Purchase #2 $62.46   10.303%   $68.8953   $68.90   $68.90   $68.90  
  Purchase #3 $133.37   9.258%   $145.7174   $145.72   $145.70   $145.70  
  Purchase #4 $211.63   6.757%   $225.9298   $225.93   $225.95   $225.90  
  Purchase #5 $145.33   10.303%   $160.3033   $160.30   $160.30   $160.30  
  Purchase #6 $98.91   8.739%   $107.5537   $107.55   $107.55   $107.60  
  Purchase #7 $79.26   10.856%   $87.8645   $87.86   $87.85   $87.90  
  7 purchase totals = $975.22       $1,065.6168   $1,065.61   $1,065.60   $1,065.70