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	$176.61	5.314%	$185.9951	$186.00	$186.00	$186.00
Purchase #2	$198.38	9.730%	$217.6824	$217.68	$217.70	$217.70
Purchase #3	$48.53	7.353%	$52.0984	$52.10	$52.10	$52.10
Purchase #4	$104.84	4.853%	$109.9279	$109.93	$109.95	$109.90
Purchase #5	$92.86	3.379%	$95.9977	$96.00	$96.00	$96.00
Purchase #6	$55.92	10.148%	$61.5948	$61.59	$61.60	$61.60
Purchase #7	$173.81	13.205%	$196.7616	$196.76	$196.75	$196.80
7 purchase totals =	$850.95		$920.0579	$920.06	$920.10	$920.10