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	$193.61	7.681%	$208.4812	$208.48	$208.50	$208.50
Purchase #2	$162.91	3.603%	$168.7796	$168.78	$168.80	$168.80
Purchase #3	$209.45	4.440%	$218.7496	$218.75	$218.75	$218.70
Purchase #4	$201.97	3.391%	$208.8188	$208.82	$208.80	$208.80
Purchase #5	$95.50	8.258%	$103.3864	$103.39	$103.40	$103.40
Purchase #6	$102.71	13.388%	$116.4608	$116.46	$116.45	$116.50
Purchase #7	$85.59	4.818%	$89.7137	$89.71	$89.70	$89.70
7 purchase totals =	$1,051.74		$1,114.3901	$1,114.39	$1,114.40	$1,114.40