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	$194.53	10.377%	$214.7164	$214.72	$214.70	$214.70
Purchase #2	$111.43	11.120%	$123.821	$123.82	$123.80	$123.80
Purchase #3	$103.86	5.218%	$109.2794	$109.28	$109.30	$109.30
Purchase #4	$91.60	7.671%	$98.6266	$98.63	$98.65	$98.60
Purchase #5	$229.44	11.291%	$255.3461	$255.35	$255.35	$255.30
Purchase #6	$183.51	3.695%	$190.2907	$190.29	$190.30	$190.30
Purchase #7	$171.32	10.758%	$189.7506	$189.75	$189.75	$189.80
7 purchase totals =	$1,085.69		$1,181.8308	$1,181.84	$1,181.85	$1,181.80