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	$22.87	3.748%	$23.7272	$23.73	$23.75	$23.70
Purchase #2	$65.68	4.789%	$68.8254	$68.83	$68.85	$68.80
Purchase #3	$187.54	4.628%	$196.2194	$196.22	$196.20	$196.20
Purchase #4	$199.80	4.449%	$208.6891	$208.69	$208.70	$208.70
Purchase #5	$103.46	7.770%	$111.4988	$111.50	$111.50	$111.50
Purchase #6	$185.61	4.253%	$193.504	$193.50	$193.50	$193.50
Purchase #7	$205.36	7.243%	$220.2342	$220.23	$220.25	$220.20
7 purchase totals =	$970.32		$1,022.6981	$1,022.70	$1,022.75	$1,022.60