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	$180.79	10.763%	$200.2484	$200.25	$200.25	$200.20
Purchase #2	$97.50	3.739%	$101.1455	$101.15	$101.15	$101.10
Purchase #3	$158.26	4.527%	$165.4244	$165.42	$165.40	$165.40
Purchase #4	$40.87	7.200%	$43.8126	$43.81	$43.80	$43.80
Purchase #5	$180.62	3.744%	$187.3824	$187.38	$187.40	$187.40
Purchase #6	$91.86	9.708%	$100.7778	$100.78	$100.80	$100.80
Purchase #7	$196.30	4.356%	$204.8508	$204.85	$204.85	$204.90
7 purchase totals =	$946.20		$1,003.6419	$1,003.64	$1,003.65	$1,003.60