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 $214.66   3.804%   $222.8257   $222.83   $222.85   $222.80  
  Purchase #2 $114.89   9.632%   $125.9562   $125.96   $125.95   $126.00  
  Purchase #3 $119.51   6.188%   $126.9053   $126.91   $126.90   $126.90  
  Purchase #4 $114.45   4.268%   $119.3347   $119.33   $119.35   $119.30  
  Purchase #5 $206.63   9.751%   $226.7785   $226.78   $226.80   $226.80  
  Purchase #6 $194.37   13.714%   $221.0259   $221.03   $221.05   $221.00  
  Purchase #7 $45.52   8.525%   $49.4006   $49.40   $49.40   $49.40  
  7 purchase totals = $1,010.03       $1,092.2269   $1,092.24   $1,092.30   $1,092.20