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	$194.90	13.866%	$221.9248	$221.92	$221.90	$221.90
Purchase #2	$130.56	10.850%	$144.7258	$144.73	$144.75	$144.70
Purchase #3	$200.76	10.479%	$221.7976	$221.80	$221.80	$221.80
Purchase #4	$231.38	10.590%	$255.8831	$255.88	$255.90	$255.90
Purchase #5	$29.64	5.551%	$31.2853	$31.29	$31.30	$31.30
Purchase #6	$126.67	3.178%	$130.6956	$130.70	$130.70	$130.70
Purchase #7	$20.52	3.658%	$21.2706	$21.27	$21.25	$21.30
7 purchase totals =	$934.43		$1,027.5828	$1,027.59	$1,027.60	$1,027.60