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	$238.96	4.361%	$249.381	$249.38	$249.40	$249.40
Purchase #2	$204.40	9.225%	$223.2559	$223.26	$223.25	$223.30
Purchase #3	$38.58	12.120%	$43.2559	$43.26	$43.25	$43.30
Purchase #4	$180.98	6.871%	$193.4151	$193.42	$193.40	$193.40
Purchase #5	$40.89	3.682%	$42.3956	$42.40	$42.40	$42.40
Purchase #6	$42.71	8.734%	$46.4403	$46.44	$46.45	$46.40
Purchase #7	$215.72	12.607%	$242.9158	$242.92	$242.90	$242.90
7 purchase totals =	$962.24		$1,041.0596	$1,041.08	$1,041.05	$1,041.10