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	$167.58	12.536%	$188.5878	$188.59	$188.60	$188.60
Purchase #2	$223.52	3.268%	$230.8246	$230.82	$230.80	$230.80
Purchase #3	$25.42	11.341%	$28.3029	$28.30	$28.30	$28.30
Purchase #4	$29.83	11.741%	$33.3323	$33.33	$33.35	$33.30
Purchase #5	$191.89	13.252%	$217.3193	$217.32	$217.30	$217.30
Purchase #6	$177.70	4.713%	$186.075	$186.08	$186.10	$186.10
Purchase #7	$124.45	12.479%	$139.9801	$139.98	$140.00	$140.00
7 purchase totals =	$940.39		$1,024.4220	$1,024.42	$1,024.45	$1,024.40