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	$230.91	10.385%	$254.89	$254.89	$254.90	$254.90
Purchase #2	$206.46	4.295%	$215.3275	$215.33	$215.35	$215.30
Purchase #3	$27.99	11.369%	$31.1722	$31.17	$31.15	$31.20
Purchase #4	$42.47	9.757%	$46.6138	$46.61	$46.60	$46.60
Purchase #5	$59.57	8.516%	$64.643	$64.64	$64.65	$64.60
Purchase #6	$139.66	10.745%	$154.6665	$154.67	$154.65	$154.70
Purchase #7	$34.42	10.462%	$38.021	$38.02	$38.00	$38.00
7 purchase totals =	$741.48		$805.3340	$805.33	$805.30	$805.30