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	$101.75	5.689%	$107.5386	$107.54	$107.55	$107.50
Purchase #2	$235.31	13.330%	$266.6768	$266.68	$266.70	$266.70
Purchase #3	$239.32	10.344%	$264.0753	$264.08	$264.10	$264.10
Purchase #4	$100.26	10.783%	$111.071	$111.07	$111.05	$111.10
Purchase #5	$211.86	11.839%	$236.9421	$236.94	$236.95	$236.90
Purchase #6	$39.42	7.252%	$42.2787	$42.28	$42.30	$42.30
Purchase #7	$104.49	13.274%	$118.36	$118.36	$118.35	$118.40
7 purchase totals =	$1,032.41		$1,146.9425	$1,146.95	$1,147.00	$1,147.00