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	$111.71	6.859%	$119.3722	$119.37	$119.35	$119.40
Purchase #2	$11.34	10.297%	$12.5077	$12.51	$12.50	$12.50
Purchase #3	$86.97	13.610%	$98.8066	$98.81	$98.80	$98.80
Purchase #4	$131.97	13.831%	$150.2228	$150.22	$150.20	$150.20
Purchase #5	$178.84	8.534%	$194.1022	$194.10	$194.10	$194.10
Purchase #6	$29.51	11.191%	$32.8125	$32.81	$32.80	$32.80
Purchase #7	$68.50	13.158%	$77.5132	$77.51	$77.50	$77.50
7 purchase totals =	$618.84		$685.3372	$685.33	$685.25	$685.30