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	$157.86	3.149%	$162.831	$162.83	$162.85	$162.80
Purchase #2	$198.54	8.605%	$215.6244	$215.62	$215.60	$215.60
Purchase #3	$218.51	3.755%	$226.7151	$226.72	$226.70	$226.70
Purchase #4	$87.42	13.276%	$99.0259	$99.03	$99.05	$99.00
Purchase #5	$234.67	12.211%	$263.3256	$263.33	$263.35	$263.30
Purchase #6	$127.47	13.859%	$145.1361	$145.14	$145.15	$145.10
Purchase #7	$56.66	9.312%	$61.9362	$61.94	$61.95	$61.90
7 purchase totals =	$1,081.13		$1,174.5943	$1,174.61	$1,174.65	$1,174.40