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	$176.51	10.729%	$195.4478	$195.45	$195.45	$195.40
Purchase #2	$85.71	3.874%	$89.0304	$89.03	$89.05	$89.00
Purchase #3	$146.31	10.477%	$161.6389	$161.64	$161.65	$161.60
Purchase #4	$222.30	5.818%	$235.2334	$235.23	$235.25	$235.20
Purchase #5	$244.64	5.816%	$258.8683	$258.87	$258.85	$258.90
Purchase #6	$211.69	5.541%	$223.4197	$223.42	$223.40	$223.40
Purchase #7	$38.38	12.704%	$43.2558	$43.26	$43.25	$43.30
7 purchase totals =	$1,125.54		$1,206.8943	$1,206.90	$1,206.90	$1,206.80