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	$222.46	8.328%	$240.9865	$240.99	$241.00	$241.00
Purchase #2	$180.72	7.126%	$193.5981	$193.60	$193.60	$193.60
Purchase #3	$51.49	5.780%	$54.4661	$54.47	$54.45	$54.50
Purchase #4	$248.90	4.244%	$259.4633	$259.46	$259.45	$259.50
Purchase #5	$102.73	8.372%	$111.3306	$111.33	$111.35	$111.30
Purchase #6	$98.30	13.475%	$111.5459	$111.55	$111.55	$111.50
Purchase #7	$219.89	6.617%	$234.4401	$234.44	$234.45	$234.40
7 purchase totals =	$1,124.49		$1,205.8306	$1,205.84	$1,205.85	$1,205.80