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	$52.29	12.104%	$58.6192	$58.62	$58.60	$58.60
Purchase #2	$106.58	4.417%	$111.2876	$111.29	$111.30	$111.30
Purchase #3	$50.85	6.768%	$54.2915	$54.29	$54.30	$54.30
Purchase #4	$82.40	8.423%	$89.3406	$89.34	$89.35	$89.30
Purchase #5	$206.66	9.220%	$225.7141	$225.71	$225.70	$225.70
Purchase #6	$107.59	6.402%	$114.4779	$114.48	$114.50	$114.50
Purchase #7	$204.90	3.359%	$211.7826	$211.78	$211.80	$211.80
7 purchase totals =	$811.27		$865.5135	$865.51	$865.55	$865.50