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	$105.99	4.540%	$110.8019	$110.80	$110.80	$110.80
Purchase #2	$138.83	6.483%	$147.8303	$147.83	$147.85	$147.80
Purchase #3	$88.82	6.493%	$94.5871	$94.59	$94.60	$94.60
Purchase #4	$56.75	5.256%	$59.7328	$59.73	$59.75	$59.70
Purchase #5	$102.99	6.700%	$109.8903	$109.89	$109.90	$109.90
Purchase #6	$155.93	5.382%	$164.3222	$164.32	$164.30	$164.30
Purchase #7	$17.40	7.322%	$18.674	$18.67	$18.65	$18.70
7 purchase totals =	$666.71		$705.8386	$705.83	$705.85	$705.80