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	$23.67	7.535%	$25.4535	$25.45	$25.45	$25.50
Purchase #2	$104.63	9.678%	$114.7561	$114.76	$114.75	$114.80
Purchase #3	$87.86	3.367%	$90.8182	$90.82	$90.80	$90.80
Purchase #4	$48.95	7.500%	$52.6213	$52.62	$52.60	$52.60
Purchase #5	$21.96	8.864%	$23.9065	$23.91	$23.90	$23.90
Purchase #6	$199.30	6.140%	$211.537	$211.54	$211.55	$211.50
Purchase #7	$223.90	13.585%	$254.3168	$254.32	$254.30	$254.30
7 purchase totals =	$710.27		$773.4094	$773.42	$773.35	$773.40