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	$185.72	11.420%	$206.9292	$206.93	$206.95	$206.90
Purchase #2	$199.52	7.865%	$215.2122	$215.21	$215.20	$215.20
Purchase #3	$185.93	4.839%	$194.9272	$194.93	$194.95	$194.90
Purchase #4	$51.55	11.751%	$57.6076	$57.61	$57.60	$57.60
Purchase #5	$156.91	6.186%	$166.6165	$166.62	$166.60	$166.60
Purchase #6	$201.47	3.422%	$208.3643	$208.36	$208.35	$208.40
Purchase #7	$48.78	3.822%	$50.6444	$50.64	$50.65	$50.60
7 purchase totals =	$1,029.88		$1,100.3014	$1,100.30	$1,100.30	$1,100.20