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	$155.40	4.279%	$162.0496	$162.05	$162.05	$162.00
Purchase #2	$213.77	7.855%	$230.5616	$230.56	$230.55	$230.60
Purchase #3	$78.72	3.222%	$81.2564	$81.26	$81.25	$81.30
Purchase #4	$187.33	6.832%	$200.1284	$200.13	$200.15	$200.10
Purchase #5	$37.50	3.468%	$38.8005	$38.80	$38.80	$38.80
Purchase #6	$134.85	3.257%	$139.2421	$139.24	$139.25	$139.20
Purchase #7	$59.87	12.847%	$67.5615	$67.56	$67.55	$67.60
7 purchase totals =	$867.44		$919.6001	$919.60	$919.60	$919.60