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	$224.78	4.604%	$235.1289	$235.13	$235.15	$235.10
Purchase #2	$42.60	7.283%	$45.7026	$45.70	$45.70	$45.70
Purchase #3	$201.54	6.573%	$214.7872	$214.79	$214.80	$214.80
Purchase #4	$117.31	3.759%	$121.7197	$121.72	$121.70	$121.70
Purchase #5	$31.73	5.570%	$33.4974	$33.50	$33.50	$33.50
Purchase #6	$162.72	10.108%	$179.1677	$179.17	$179.15	$179.20
Purchase #7	$166.83	3.864%	$173.2763	$173.28	$173.30	$173.30
7 purchase totals =	$947.51		$1,003.2798	$1,003.29	$1,003.30	$1,003.30