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	$250.37	6.603%	$266.9019	$266.90	$266.90	$266.90
Purchase #2	$96.88	3.685%	$100.45	$100.45	$100.45	$100.50
Purchase #3	$25.85	11.708%	$28.8765	$28.88	$28.90	$28.90
Purchase #4	$94.49	6.519%	$100.6498	$100.65	$100.65	$100.60
Purchase #5	$244.69	5.692%	$258.6178	$258.62	$258.60	$258.60
Purchase #6	$56.31	3.567%	$58.3186	$58.32	$58.30	$58.30
Purchase #7	$206.97	12.687%	$233.2283	$233.23	$233.25	$233.20
7 purchase totals =	$975.56		$1,047.0429	$1,047.05	$1,047.05	$1,047.00