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	$171.86	11.227%	$191.1547	$191.15	$191.15	$191.20
Purchase #2	$47.79	12.713%	$53.8655	$53.87	$53.85	$53.90
Purchase #3	$93.98	6.722%	$100.2973	$100.30	$100.30	$100.30
Purchase #4	$219.88	4.606%	$230.0077	$230.01	$230.00	$230.00
Purchase #5	$248.98	12.236%	$279.4452	$279.45	$279.45	$279.40
Purchase #6	$42.57	6.428%	$45.3064	$45.31	$45.30	$45.30
Purchase #7	$33.49	3.520%	$34.6688	$34.67	$34.65	$34.70
7 purchase totals =	$858.55		$934.7456	$934.76	$934.70	$934.80