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	$171.52	8.232%	$185.6395	$185.64	$185.65	$185.60
Purchase #2	$146.68	5.246%	$154.3748	$154.37	$154.35	$154.40
Purchase #3	$78.49	12.729%	$88.481	$88.48	$88.50	$88.50
Purchase #4	$167.86	4.147%	$174.8212	$174.82	$174.80	$174.80
Purchase #5	$143.50	13.408%	$162.7405	$162.74	$162.75	$162.70
Purchase #6	$179.84	5.148%	$189.0982	$189.10	$189.10	$189.10
Purchase #7	$57.72	8.301%	$62.5113	$62.51	$62.50	$62.50
7 purchase totals =	$945.61		$1,017.6665	$1,017.66	$1,017.65	$1,017.60