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	$115.30	3.119%	$118.8962	$118.90	$118.90	$118.90
Purchase #2	$46.70	13.487%	$52.9984	$53.00	$53.00	$53.00
Purchase #3	$63.39	6.361%	$67.4222	$67.42	$67.40	$67.40
Purchase #4	$101.72	12.397%	$114.3302	$114.33	$114.35	$114.30
Purchase #5	$232.42	11.472%	$259.0832	$259.08	$259.10	$259.10
Purchase #6	$185.31	11.653%	$206.9042	$206.90	$206.90	$206.90
Purchase #7	$244.93	4.858%	$256.8287	$256.83	$256.85	$256.80
7 purchase totals =	$989.77		$1,076.4631	$1,076.46	$1,076.50	$1,076.40