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	$200.31	8.746%	$217.8291	$217.83	$217.85	$217.80
Purchase #2	$33.91	10.266%	$37.3912	$37.39	$37.40	$37.40
Purchase #3	$88.52	4.442%	$92.4521	$92.45	$92.45	$92.50
Purchase #4	$207.46	11.174%	$230.6416	$230.64	$230.65	$230.60
Purchase #5	$180.34	9.524%	$197.5156	$197.52	$197.50	$197.50
Purchase #6	$60.62	6.536%	$64.5821	$64.58	$64.60	$64.60
Purchase #7	$181.50	5.736%	$191.9108	$191.91	$191.90	$191.90
7 purchase totals =	$952.66		$1,032.3225	$1,032.32	$1,032.35	$1,032.30