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	$145.82	3.669%	$151.1701	$151.17	$151.15	$151.20
Purchase #2	$55.75	11.783%	$62.319	$62.32	$62.30	$62.30
Purchase #3	$42.47	6.555%	$45.2539	$45.25	$45.25	$45.30
Purchase #4	$233.93	12.156%	$262.3665	$262.37	$262.35	$262.40
Purchase #5	$68.76	10.189%	$75.766	$75.77	$75.75	$75.80
Purchase #6	$231.96	11.839%	$259.4217	$259.42	$259.40	$259.40
Purchase #7	$97.72	3.585%	$101.2233	$101.22	$101.20	$101.20
7 purchase totals =	$876.41		$957.5205	$957.52	$957.40	$957.60