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	$199.58	7.596%	$214.7401	$214.74	$214.75	$214.70
Purchase #2	$110.57	5.697%	$116.8692	$116.87	$116.85	$116.90
Purchase #3	$66.27	8.209%	$71.7101	$71.71	$71.70	$71.70
Purchase #4	$59.33	3.280%	$61.276	$61.28	$61.30	$61.30
Purchase #5	$233.71	13.474%	$265.2001	$265.20	$265.20	$265.20
Purchase #6	$217.76	7.151%	$233.332	$233.33	$233.35	$233.30
Purchase #7	$51.62	9.486%	$56.5167	$56.52	$56.50	$56.50
7 purchase totals =	$938.84		$1,019.6442	$1,019.65	$1,019.65	$1,019.60