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	$23.76	5.432%	$25.0506	$25.05	$25.05	$25.10
Purchase #2	$174.60	11.407%	$194.5166	$194.52	$194.50	$194.50
Purchase #3	$115.28	10.594%	$127.4928	$127.49	$127.50	$127.50
Purchase #4	$49.53	3.401%	$51.2145	$51.21	$51.20	$51.20
Purchase #5	$87.45	4.761%	$91.6135	$91.61	$91.60	$91.60
Purchase #6	$173.39	4.799%	$181.711	$181.71	$181.70	$181.70
Purchase #7	$95.54	10.761%	$105.8211	$105.82	$105.80	$105.80
7 purchase totals =	$719.55		$777.4201	$777.41	$777.35	$777.40