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	$37.65	8.143%	$40.7158	$40.72	$40.70	$40.70
Purchase #2	$173.78	13.241%	$196.7902	$196.79	$196.80	$196.80
Purchase #3	$44.60	4.786%	$46.7346	$46.73	$46.75	$46.70
Purchase #4	$111.83	3.110%	$115.3079	$115.31	$115.30	$115.30
Purchase #5	$111.49	13.216%	$126.2245	$126.22	$126.20	$126.20
Purchase #6	$109.52	9.506%	$119.931	$119.93	$119.95	$119.90
Purchase #7	$73.30	6.559%	$78.1077	$78.11	$78.10	$78.10
7 purchase totals =	$662.17		$723.8117	$723.81	$723.80	$723.70