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	$115.58	3.236%	$119.3202	$119.32	$119.30	$119.30
Purchase #2	$24.50	4.259%	$25.5435	$25.54	$25.55	$25.50
Purchase #3	$65.35	3.859%	$67.8719	$67.87	$67.85	$67.90
Purchase #4	$40.95	5.196%	$43.0778	$43.08	$43.10	$43.10
Purchase #5	$132.95	3.346%	$137.3985	$137.40	$137.40	$137.40
Purchase #6	$230.27	3.580%	$238.5137	$238.51	$238.50	$238.50
Purchase #7	$152.40	8.287%	$165.0294	$165.03	$165.05	$165.00
7 purchase totals =	$762.00		$796.7550	$796.75	$796.75	$796.70