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	$155.33	3.802%	$161.2356	$161.24	$161.25	$161.20
Purchase #2	$134.85	7.240%	$144.6131	$144.61	$144.60	$144.60
Purchase #3	$146.49	5.361%	$154.3433	$154.34	$154.35	$154.30
Purchase #4	$160.71	8.654%	$174.6178	$174.62	$174.60	$174.60
Purchase #5	$10.73	6.565%	$11.4344	$11.43	$11.45	$11.40
Purchase #6	$214.37	6.114%	$227.4766	$227.48	$227.50	$227.50
Purchase #7	$218.84	3.491%	$226.4797	$226.48	$226.50	$226.50
7 purchase totals =	$1,041.32		$1,100.2005	$1,100.20	$1,100.25	$1,100.10