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	$168.67	5.823%	$178.4917	$178.49	$178.50	$178.50
Purchase #2	$34.32	11.514%	$38.2716	$38.27	$38.25	$38.30
Purchase #3	$161.62	7.818%	$174.2555	$174.26	$174.25	$174.30
Purchase #4	$18.27	5.206%	$19.2211	$19.22	$19.20	$19.20
Purchase #5	$54.82	8.378%	$59.4128	$59.41	$59.40	$59.40
Purchase #6	$203.89	6.469%	$217.0796	$217.08	$217.10	$217.10
Purchase #7	$103.39	9.844%	$113.5677	$113.57	$113.55	$113.60
7 purchase totals =	$744.98		$800.3000	$800.30	$800.25	$800.40