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	$92.31	7.168%	$98.9268	$98.93	$98.95	$98.90
Purchase #2	$133.66	7.362%	$143.5	$143.50	$143.50	$143.50
Purchase #3	$145.64	11.708%	$162.6915	$162.69	$162.70	$162.70
Purchase #4	$249.87	4.613%	$261.3965	$261.40	$261.40	$261.40
Purchase #5	$158.99	5.598%	$167.8903	$167.89	$167.90	$167.90
Purchase #6	$163.47	3.191%	$168.6863	$168.69	$168.70	$168.70
Purchase #7	$54.94	11.785%	$61.4147	$61.41	$61.40	$61.40
7 purchase totals =	$998.88		$1,064.5061	$1,064.51	$1,064.55	$1,064.50