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	$80.64	5.737%	$85.2663	$85.27	$85.25	$85.30
Purchase #2	$205.36	5.732%	$217.1312	$217.13	$217.15	$217.10
Purchase #3	$102.94	3.448%	$106.4894	$106.49	$106.50	$106.50
Purchase #4	$164.66	7.262%	$176.6176	$176.62	$176.60	$176.60
Purchase #5	$196.59	7.763%	$211.8513	$211.85	$211.85	$211.90
Purchase #6	$153.32	13.104%	$173.4111	$173.41	$173.40	$173.40
Purchase #7	$54.98	8.624%	$59.7215	$59.72	$59.70	$59.70
7 purchase totals =	$958.49		$1,030.4884	$1,030.49	$1,030.45	$1,030.50