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	$198.99	11.255%	$221.3863	$221.39	$221.40	$221.40
Purchase #2	$86.32	12.263%	$96.9054	$96.91	$96.90	$96.90
Purchase #3	$38.37	13.736%	$43.6405	$43.64	$43.65	$43.60
Purchase #4	$107.93	3.702%	$111.9256	$111.93	$111.95	$111.90
Purchase #5	$41.76	13.144%	$47.2489	$47.25	$47.25	$47.20
Purchase #6	$172.52	11.621%	$192.5685	$192.57	$192.55	$192.60
Purchase #7	$223.45	9.446%	$244.5571	$244.56	$244.55	$244.60
7 purchase totals =	$869.34		$958.2323	$958.25	$958.25	$958.20