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	$101.57	9.379%	$111.0963	$111.10	$111.10	$111.10
Purchase #2	$181.94	4.561%	$190.2383	$190.24	$190.25	$190.20
Purchase #3	$159.82	12.633%	$180.0101	$180.01	$180.00	$180.00
Purchase #4	$67.78	12.809%	$76.4619	$76.46	$76.45	$76.50
Purchase #5	$80.39	12.553%	$90.4814	$90.48	$90.50	$90.50
Purchase #6	$39.90	3.859%	$41.4397	$41.44	$41.45	$41.40
Purchase #7	$68.30	3.442%	$70.6509	$70.65	$70.65	$70.70
7 purchase totals =	$699.70		$760.3786	$760.38	$760.40	$760.40