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	$54.72	13.643%	$62.1854	$62.19	$62.20	$62.20
Purchase #2	$101.56	3.385%	$104.9978	$105.00	$105.00	$105.00
Purchase #3	$197.30	6.847%	$210.8091	$210.81	$210.80	$210.80
Purchase #4	$187.47	6.328%	$199.3331	$199.33	$199.35	$199.30
Purchase #5	$101.96	3.136%	$105.1575	$105.16	$105.15	$105.20
Purchase #6	$120.67	10.418%	$133.2414	$133.24	$133.25	$133.20
Purchase #7	$101.70	9.848%	$111.7154	$111.72	$111.70	$111.70
7 purchase totals =	$865.38		$927.4397	$927.45	$927.45	$927.40