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	$50.48	4.532%	$52.7678	$52.77	$52.75	$52.80
Purchase #2	$164.53	5.291%	$173.2353	$173.24	$173.25	$173.20
Purchase #3	$97.70	12.132%	$109.553	$109.55	$109.55	$109.60
Purchase #4	$49.57	7.109%	$53.0939	$53.09	$53.10	$53.10
Purchase #5	$143.73	8.187%	$155.4972	$155.50	$155.50	$155.50
Purchase #6	$47.72	7.811%	$51.4474	$51.45	$51.45	$51.40
Purchase #7	$37.29	9.222%	$40.7289	$40.73	$40.75	$40.70
7 purchase totals =	$591.02		$636.3235	$636.33	$636.35	$636.30